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	$60.48	3.400%	$62.5363	$62.54	$62.55	$62.50
Purchase #2	$58.80	4.857%	$61.6559	$61.66	$61.65	$61.70
Purchase #3	$98.40	10.474%	$108.7064	$108.71	$108.70	$108.70
Purchase #4	$39.38	5.632%	$41.5979	$41.60	$41.60	$41.60
Purchase #5	$238.83	4.105%	$248.634	$248.63	$248.65	$248.60
Purchase #6	$49.47	11.486%	$55.1521	$55.15	$55.15	$55.20
Purchase #7	$226.50	12.607%	$255.0549	$255.05	$255.05	$255.10
7 purchase totals =	$771.86		$833.3375	$833.34	$833.35	$833.40