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	$125.76	6.306%	$133.6904	$133.69	$133.70	$133.70
Purchase #2	$59.91	3.769%	$62.168	$62.17	$62.15	$62.20
Purchase #3	$109.28	4.434%	$114.1255	$114.13	$114.15	$114.10
Purchase #4	$249.98	9.474%	$273.6631	$273.66	$273.65	$273.70
Purchase #5	$71.45	9.778%	$78.4364	$78.44	$78.45	$78.40
Purchase #6	$102.52	5.485%	$108.1432	$108.14	$108.15	$108.10
Purchase #7	$164.92	10.145%	$181.6511	$181.65	$181.65	$181.70
7 purchase totals =	$883.82		$951.8777	$951.88	$951.90	$951.90