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	$94.96	5.144%	$99.8447	$99.84	$99.85	$99.80
Purchase #2	$217.33	4.614%	$227.3576	$227.36	$227.35	$227.40
Purchase #3	$168.70	6.131%	$179.043	$179.04	$179.05	$179.00
Purchase #4	$214.74	5.553%	$226.6645	$226.66	$226.65	$226.70
Purchase #5	$55.44	10.196%	$61.0927	$61.09	$61.10	$61.10
Purchase #6	$118.86	5.148%	$124.9789	$124.98	$125.00	$125.00
Purchase #7	$155.86	7.217%	$167.1084	$167.11	$167.10	$167.10
7 purchase totals =	$1,025.89		$1,086.0898	$1,086.08	$1,086.10	$1,086.10