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	$158.42	13.526%	$179.8479	$179.85	$179.85	$179.80
Purchase #2	$151.91	12.626%	$171.0902	$171.09	$171.10	$171.10
Purchase #3	$10.64	7.382%	$11.4254	$11.43	$11.45	$11.40
Purchase #4	$64.27	9.447%	$70.3416	$70.34	$70.35	$70.30
Purchase #5	$202.89	12.587%	$228.4278	$228.43	$228.45	$228.40
Purchase #6	$57.32	3.502%	$59.3273	$59.33	$59.35	$59.30
Purchase #7	$115.34	9.109%	$125.8463	$125.85	$125.85	$125.80
7 purchase totals =	$760.79		$846.3065	$846.32	$846.40	$846.10