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	$31.63	4.227%	$32.967	$32.97	$32.95	$33.00
Purchase #2	$183.45	13.779%	$208.7276	$208.73	$208.75	$208.70
Purchase #3	$157.43	4.829%	$165.0323	$165.03	$165.05	$165.00
Purchase #4	$41.26	10.425%	$45.5614	$45.56	$45.55	$45.60
Purchase #5	$78.88	12.648%	$88.8567	$88.86	$88.85	$88.90
Purchase #6	$113.54	3.852%	$117.9136	$117.91	$117.90	$117.90
Purchase #7	$88.89	12.531%	$100.0288	$100.03	$100.05	$100.00
7 purchase totals =	$695.08		$759.0874	$759.09	$759.10	$759.10