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	$202.78	4.635%	$212.1789	$212.18	$212.20	$212.20
Purchase #2	$30.96	5.124%	$32.5464	$32.55	$32.55	$32.50
Purchase #3	$245.83	6.629%	$262.1261	$262.13	$262.15	$262.10
Purchase #4	$87.51	4.508%	$91.455	$91.46	$91.45	$91.50
Purchase #5	$57.81	8.189%	$62.5441	$62.54	$62.55	$62.50
Purchase #6	$173.46	13.461%	$196.8095	$196.81	$196.80	$196.80
Purchase #7	$211.71	10.666%	$234.291	$234.29	$234.30	$234.30
7 purchase totals =	$1,010.06		$1,091.9510	$1,091.96	$1,092.00	$1,091.90