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	$158.25	3.779%	$164.2303	$164.23	$164.25	$164.20
Purchase #2	$166.87	5.208%	$175.5606	$175.56	$175.55	$175.60
Purchase #3	$107.64	4.524%	$112.5096	$112.51	$112.50	$112.50
Purchase #4	$142.65	5.175%	$150.0321	$150.03	$150.05	$150.00
Purchase #5	$239.53	10.107%	$263.7393	$263.74	$263.75	$263.70
Purchase #6	$79.97	13.161%	$90.4949	$90.49	$90.50	$90.50
Purchase #7	$51.41	5.469%	$54.2216	$54.22	$54.20	$54.20
7 purchase totals =	$946.32		$1,010.7884	$1,010.78	$1,010.80	$1,010.70