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	$58.32	11.692%	$65.1388	$65.14	$65.15	$65.10
Purchase #2	$184.34	3.706%	$191.1716	$191.17	$191.15	$191.20
Purchase #3	$178.46	5.710%	$188.6501	$188.65	$188.65	$188.70
Purchase #4	$233.41	9.748%	$256.1628	$256.16	$256.15	$256.20
Purchase #5	$216.82	11.682%	$242.1489	$242.15	$242.15	$242.10
Purchase #6	$71.50	10.696%	$79.1476	$79.15	$79.15	$79.10
Purchase #7	$114.69	11.418%	$127.7853	$127.79	$127.80	$127.80
7 purchase totals =	$1,057.54		$1,150.2051	$1,150.21	$1,150.20	$1,150.20