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	$110.72	13.607%	$125.7857	$125.79	$125.80	$125.80
Purchase #2	$47.93	13.341%	$54.3243	$54.32	$54.30	$54.30
Purchase #3	$65.72	10.710%	$72.7586	$72.76	$72.75	$72.80
Purchase #4	$164.70	6.667%	$175.6805	$175.68	$175.70	$175.70
Purchase #5	$249.76	5.614%	$263.7815	$263.78	$263.80	$263.80
Purchase #6	$197.72	5.800%	$209.1878	$209.19	$209.20	$209.20
Purchase #7	$99.75	5.784%	$105.5195	$105.52	$105.50	$105.50
7 purchase totals =	$936.30		$1,007.0379	$1,007.04	$1,007.05	$1,007.10