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	$199.35	13.632%	$226.5254	$226.53	$226.55	$226.50
Purchase #2	$68.79	3.448%	$71.1619	$71.16	$71.15	$71.20
Purchase #3	$42.50	6.522%	$45.2719	$45.27	$45.25	$45.30
Purchase #4	$93.61	9.671%	$102.663	$102.66	$102.65	$102.70
Purchase #5	$111.84	11.701%	$124.9264	$124.93	$124.95	$124.90
Purchase #6	$49.28	5.766%	$52.1215	$52.12	$52.10	$52.10
Purchase #7	$92.78	13.780%	$105.5651	$105.57	$105.55	$105.60
7 purchase totals =	$658.15		$728.2352	$728.24	$728.20	$728.30