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	$131.53	6.258%	$139.7611	$139.76	$139.75	$139.80
Purchase #2	$122.26	4.663%	$127.961	$127.96	$127.95	$128.00
Purchase #3	$96.39	8.370%	$104.4578	$104.46	$104.45	$104.50
Purchase #4	$167.41	10.210%	$184.5026	$184.50	$184.50	$184.50
Purchase #5	$32.50	3.531%	$33.6476	$33.65	$33.65	$33.60
Purchase #6	$111.33	13.307%	$126.1447	$126.14	$126.15	$126.10
Purchase #7	$14.38	3.258%	$14.8485	$14.85	$14.85	$14.80
7 purchase totals =	$675.80		$731.3233	$731.32	$731.30	$731.30