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	$10.98	3.252%	$11.3371	$11.34	$11.35	$11.30
Purchase #2	$88.47	8.796%	$96.2518	$96.25	$96.25	$96.30
Purchase #3	$40.39	11.760%	$45.1399	$45.14	$45.15	$45.10
Purchase #4	$112.83	12.726%	$127.1887	$127.19	$127.20	$127.20
Purchase #5	$166.98	9.863%	$183.4492	$183.45	$183.45	$183.40
Purchase #6	$50.39	10.210%	$55.5348	$55.53	$55.55	$55.50
Purchase #7	$118.60	9.133%	$129.4317	$129.43	$129.45	$129.40
7 purchase totals =	$588.64		$648.3332	$648.33	$648.40	$648.20