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	$40.41	11.502%	$45.058	$45.06	$45.05	$45.10
Purchase #2	$237.89	8.852%	$258.948	$258.95	$258.95	$258.90
Purchase #3	$50.48	4.824%	$52.9152	$52.92	$52.90	$52.90
Purchase #4	$179.71	7.569%	$193.3122	$193.31	$193.30	$193.30
Purchase #5	$134.85	11.248%	$150.0179	$150.02	$150.00	$150.00
Purchase #6	$61.36	10.537%	$67.8255	$67.83	$67.85	$67.80
Purchase #7	$196.27	7.413%	$210.8195	$210.82	$210.80	$210.80
7 purchase totals =	$900.97		$978.8963	$978.91	$978.85	$978.80