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	$124.83	3.221%	$128.8508	$128.85	$128.85	$128.90
Purchase #2	$126.87	8.654%	$137.8493	$137.85	$137.85	$137.80
Purchase #3	$90.96	8.355%	$98.5597	$98.56	$98.55	$98.60
Purchase #4	$35.64	11.159%	$39.6171	$39.62	$39.60	$39.60
Purchase #5	$209.37	12.669%	$235.8951	$235.90	$235.90	$235.90
Purchase #6	$138.30	7.412%	$148.5508	$148.55	$148.55	$148.60
Purchase #7	$250.38	8.290%	$271.1365	$271.14	$271.15	$271.10
7 purchase totals =	$976.35		$1,060.4593	$1,060.47	$1,060.45	$1,060.50