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	$79.65	8.835%	$86.6871	$86.69	$86.70	$86.70
Purchase #2	$146.70	8.480%	$159.1402	$159.14	$159.15	$159.10
Purchase #3	$118.90	7.254%	$127.525	$127.53	$127.55	$127.50
Purchase #4	$88.87	12.698%	$100.1547	$100.15	$100.15	$100.20
Purchase #5	$48.35	10.174%	$53.2691	$53.27	$53.25	$53.30
Purchase #6	$13.38	12.620%	$15.0686	$15.07	$15.05	$15.10
Purchase #7	$223.61	8.705%	$243.0753	$243.08	$243.10	$243.10
7 purchase totals =	$719.46		$784.9200	$784.93	$784.95	$785.00