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	$100.70	11.870%	$112.6531	$112.65	$112.65	$112.70
Purchase #2	$227.55	11.781%	$254.3577	$254.36	$254.35	$254.40
Purchase #3	$66.60	8.288%	$72.1198	$72.12	$72.10	$72.10
Purchase #4	$249.67	12.807%	$281.6452	$281.65	$281.65	$281.60
Purchase #5	$125.59	8.784%	$136.6218	$136.62	$136.60	$136.60
Purchase #6	$144.79	9.754%	$158.9128	$158.91	$158.90	$158.90
Purchase #7	$141.30	3.404%	$146.1099	$146.11	$146.10	$146.10
7 purchase totals =	$1,056.20		$1,162.4203	$1,162.42	$1,162.35	$1,162.40