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	$162.85	11.540%	$181.6429	$181.64	$181.65	$181.60
Purchase #2	$147.78	9.722%	$162.1472	$162.15	$162.15	$162.10
Purchase #3	$41.87	10.130%	$46.1114	$46.11	$46.10	$46.10
Purchase #4	$245.83	5.594%	$259.5817	$259.58	$259.60	$259.60
Purchase #5	$232.72	5.466%	$245.4405	$245.44	$245.45	$245.40
Purchase #6	$146.88	13.408%	$166.5737	$166.57	$166.55	$166.60
Purchase #7	$119.68	9.498%	$131.0472	$131.05	$131.05	$131.00
7 purchase totals =	$1,097.61		$1,192.5446	$1,192.54	$1,192.55	$1,192.40