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	$99.63	12.283%	$111.8676	$111.87	$111.85	$111.90
Purchase #2	$24.34	5.166%	$25.5974	$25.60	$25.60	$25.60
Purchase #3	$247.73	12.769%	$279.3626	$279.36	$279.35	$279.40
Purchase #4	$236.69	8.381%	$256.527	$256.53	$256.55	$256.50
Purchase #5	$154.64	6.238%	$164.2864	$164.29	$164.30	$164.30
Purchase #6	$149.42	12.672%	$168.3545	$168.35	$168.35	$168.40
Purchase #7	$151.41	13.473%	$171.8095	$171.81	$171.80	$171.80
7 purchase totals =	$1,063.86		$1,177.8050	$1,177.81	$1,177.80	$1,177.90