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	$244.57	11.316%	$272.2455	$272.25	$272.25	$272.20
Purchase #2	$97.68	11.146%	$108.5674	$108.57	$108.55	$108.60
Purchase #3	$74.95	10.608%	$82.9007	$82.90	$82.90	$82.90
Purchase #4	$65.43	8.363%	$70.9019	$70.90	$70.90	$70.90
Purchase #5	$239.33	10.231%	$263.8159	$263.82	$263.80	$263.80
Purchase #6	$153.91	13.279%	$174.3477	$174.35	$174.35	$174.30
Purchase #7	$78.47	6.705%	$83.7314	$83.73	$83.75	$83.70
7 purchase totals =	$954.34		$1,056.5105	$1,056.52	$1,056.50	$1,056.40