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	$85.83	5.759%	$90.7729	$90.77	$90.75	$90.80
Purchase #2	$175.99	13.680%	$200.0654	$200.07	$200.05	$200.10
Purchase #3	$67.59	5.253%	$71.1405	$71.14	$71.15	$71.10
Purchase #4	$45.52	4.314%	$47.4837	$47.48	$47.50	$47.50
Purchase #5	$209.41	3.806%	$217.3801	$217.38	$217.40	$217.40
Purchase #6	$140.43	10.718%	$155.4813	$155.48	$155.50	$155.50
Purchase #7	$162.67	11.257%	$180.9818	$180.98	$181.00	$181.00
7 purchase totals =	$887.44		$963.3057	$963.30	$963.35	$963.40