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	$172.32	13.814%	$196.1243	$196.12	$196.10	$196.10
Purchase #2	$232.27	11.219%	$258.3284	$258.33	$258.35	$258.30
Purchase #3	$7.81	11.311%	$8.6934	$8.69	$8.70	$8.70
Purchase #4	$72.80	6.283%	$77.374	$77.37	$77.35	$77.40
Purchase #5	$96.83	10.257%	$106.7619	$106.76	$106.75	$106.80
Purchase #6	$12.55	5.429%	$13.2313	$13.23	$13.25	$13.20
Purchase #7	$45.54	11.772%	$50.901	$50.90	$50.90	$50.90
7 purchase totals =	$640.12		$711.4143	$711.40	$711.40	$711.40