Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$162.42	7.393%	$174.4277	$174.43	$174.45	$174.40
Purchase #2	$149.55	6.375%	$159.0838	$159.08	$159.10	$159.10
Purchase #3	$166.43	12.496%	$187.2271	$187.23	$187.25	$187.20
Purchase #4	$170.36	8.402%	$184.6736	$184.67	$184.65	$184.70
Purchase #5	$187.51	4.834%	$196.5742	$196.57	$196.55	$196.60
Purchase #6	$245.36	5.660%	$259.2474	$259.25	$259.25	$259.20
Purchase #7	$215.53	10.566%	$238.3029	$238.30	$238.30	$238.30
7 purchase totals =	$1,297.16		$1,399.5367	$1,399.53	$1,399.55	$1,399.50