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	$191.95	13.238%	$217.3603	$217.36	$217.35	$217.40
Purchase #2	$34.93	7.404%	$37.5162	$37.52	$37.50	$37.50
Purchase #3	$54.64	5.583%	$57.6906	$57.69	$57.70	$57.70
Purchase #4	$138.92	9.641%	$152.3133	$152.31	$152.30	$152.30
Purchase #5	$43.30	5.133%	$45.5226	$45.52	$45.50	$45.50
Purchase #6	$247.58	8.156%	$267.7726	$267.77	$267.75	$267.80
Purchase #7	$156.99	9.521%	$171.937	$171.94	$171.95	$171.90
7 purchase totals =	$868.31		$950.1126	$950.11	$950.05	$950.10