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	$111.78	5.504%	$117.9324	$117.93	$117.95	$117.90
Purchase #2	$24.94	13.144%	$28.2181	$28.22	$28.20	$28.20
Purchase #3	$225.91	5.487%	$238.3057	$238.31	$238.30	$238.30
Purchase #4	$95.91	10.653%	$106.1273	$106.13	$106.15	$106.10
Purchase #5	$133.57	5.796%	$141.3117	$141.31	$141.30	$141.30
Purchase #6	$70.73	11.505%	$78.8675	$78.87	$78.85	$78.90
Purchase #7	$234.80	13.677%	$266.9136	$266.91	$266.90	$266.90
7 purchase totals =	$897.64		$977.6763	$977.68	$977.65	$977.60