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	$162.85	5.787%	$172.2741	$172.27	$172.25	$172.30
Purchase #2	$223.76	13.518%	$254.0079	$254.01	$254.00	$254.00
Purchase #3	$14.51	13.846%	$16.5191	$16.52	$16.50	$16.50
Purchase #4	$38.53	9.421%	$42.1599	$42.16	$42.15	$42.20
Purchase #5	$46.35	12.799%	$52.2823	$52.28	$52.30	$52.30
Purchase #6	$156.52	12.122%	$175.4934	$175.49	$175.50	$175.50
Purchase #7	$137.54	13.400%	$155.9704	$155.97	$155.95	$156.00
7 purchase totals =	$780.06		$868.7071	$868.70	$868.65	$868.80