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	$86.84	11.229%	$96.5913	$96.59	$96.60	$96.60
Purchase #2	$157.76	8.749%	$171.5624	$171.56	$171.55	$171.60
Purchase #3	$233.70	8.373%	$253.2677	$253.27	$253.25	$253.30
Purchase #4	$39.90	5.837%	$42.229	$42.23	$42.25	$42.20
Purchase #5	$227.69	12.619%	$256.4222	$256.42	$256.40	$256.40
Purchase #6	$120.87	3.192%	$124.7282	$124.73	$124.75	$124.70
Purchase #7	$129.35	8.790%	$140.7199	$140.72	$140.70	$140.70
7 purchase totals =	$996.11		$1,085.5207	$1,085.52	$1,085.50	$1,085.50