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	$218.87	6.150%	$232.3305	$232.33	$232.35	$232.30
Purchase #2	$7.29	8.501%	$7.9097	$7.91	$7.90	$7.90
Purchase #3	$51.41	11.122%	$57.1278	$57.13	$57.15	$57.10
Purchase #4	$138.25	11.376%	$153.9773	$153.98	$154.00	$154.00
Purchase #5	$36.75	13.391%	$41.6712	$41.67	$41.65	$41.70
Purchase #6	$98.41	10.717%	$108.9566	$108.96	$108.95	$109.00
Purchase #7	$59.74	10.337%	$65.9153	$65.92	$65.90	$65.90
7 purchase totals =	$610.72		$667.8884	$667.90	$667.90	$667.90