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	$59.85	10.824%	$66.3282	$66.33	$66.35	$66.30
Purchase #2	$238.61	13.212%	$270.1352	$270.14	$270.15	$270.10
Purchase #3	$247.91	12.872%	$279.821	$279.82	$279.80	$279.80
Purchase #4	$43.59	10.412%	$48.1286	$48.13	$48.15	$48.10
Purchase #5	$20.42	6.143%	$21.6744	$21.67	$21.65	$21.70
Purchase #6	$231.83	7.647%	$249.558	$249.56	$249.55	$249.60
Purchase #7	$192.75	10.291%	$212.5859	$212.59	$212.60	$212.60
7 purchase totals =	$1,034.96		$1,148.2313	$1,148.24	$1,148.25	$1,148.20