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	$179.66	11.276%	$199.9185	$199.92	$199.90	$199.90
Purchase #2	$41.98	3.415%	$43.4136	$43.41	$43.40	$43.40
Purchase #3	$183.69	6.817%	$196.2121	$196.21	$196.20	$196.20
Purchase #4	$20.48	13.528%	$23.2505	$23.25	$23.25	$23.30
Purchase #5	$45.96	4.674%	$48.1082	$48.11	$48.10	$48.10
Purchase #6	$101.51	4.211%	$105.7846	$105.78	$105.80	$105.80
Purchase #7	$208.91	6.200%	$221.8624	$221.86	$221.85	$221.90
7 purchase totals =	$782.19		$838.5499	$838.54	$838.50	$838.60