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	$242.44	6.289%	$257.6871	$257.69	$257.70	$257.70
Purchase #2	$34.86	5.513%	$36.7818	$36.78	$36.80	$36.80
Purchase #3	$211.86	12.414%	$238.1603	$238.16	$238.15	$238.20
Purchase #4	$72.50	7.482%	$77.9245	$77.92	$77.90	$77.90
Purchase #5	$84.72	6.520%	$90.2437	$90.24	$90.25	$90.20
Purchase #6	$189.29	7.740%	$203.941	$203.94	$203.95	$203.90
Purchase #7	$160.89	3.131%	$165.9275	$165.93	$165.95	$165.90
7 purchase totals =	$996.56		$1,070.6659	$1,070.66	$1,070.70	$1,070.60