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	$178.37	10.137%	$196.4514	$196.45	$196.45	$196.50
Purchase #2	$202.51	7.269%	$217.2305	$217.23	$217.25	$217.20
Purchase #3	$30.74	8.572%	$33.375	$33.38	$33.40	$33.40
Purchase #4	$117.63	13.251%	$133.2172	$133.22	$133.20	$133.20
Purchase #5	$197.71	7.648%	$212.8309	$212.83	$212.85	$212.80
Purchase #6	$49.72	10.472%	$54.9267	$54.93	$54.95	$54.90
Purchase #7	$228.44	9.118%	$249.2692	$249.27	$249.25	$249.30
7 purchase totals =	$1,005.12		$1,097.3009	$1,097.31	$1,097.35	$1,097.30