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	$157.98	5.367%	$166.4588	$166.46	$166.45	$166.50
Purchase #2	$12.76	12.365%	$14.3378	$14.34	$14.35	$14.30
Purchase #3	$46.27	8.339%	$50.1285	$50.13	$50.15	$50.10
Purchase #4	$113.64	12.821%	$128.2098	$128.21	$128.20	$128.20
Purchase #5	$118.46	7.432%	$127.2639	$127.26	$127.25	$127.30
Purchase #6	$230.35	4.226%	$240.0846	$240.08	$240.10	$240.10
Purchase #7	$143.85	3.473%	$148.8459	$148.85	$148.85	$148.80
7 purchase totals =	$823.31		$875.3293	$875.33	$875.35	$875.30