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	$98.37	12.380%	$110.5482	$110.55	$110.55	$110.50
Purchase #2	$196.34	3.141%	$202.507	$202.51	$202.50	$202.50
Purchase #3	$170.96	13.853%	$194.6431	$194.64	$194.65	$194.60
Purchase #4	$250.89	11.394%	$279.4764	$279.48	$279.50	$279.50
Purchase #5	$98.50	3.321%	$101.7712	$101.77	$101.75	$101.80
Purchase #6	$228.30	12.245%	$256.2553	$256.26	$256.25	$256.30
Purchase #7	$41.29	10.108%	$45.4636	$45.46	$45.45	$45.50
7 purchase totals =	$1,084.65		$1,190.6648	$1,190.67	$1,190.65	$1,190.70