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	$233.89	4.298%	$243.9426	$243.94	$243.95	$243.90
Purchase #2	$191.80	3.678%	$198.8544	$198.85	$198.85	$198.90
Purchase #3	$102.45	11.240%	$113.9654	$113.97	$113.95	$114.00
Purchase #4	$206.69	7.613%	$222.4253	$222.43	$222.45	$222.40
Purchase #5	$87.47	12.468%	$98.3758	$98.38	$98.40	$98.40
Purchase #6	$196.98	6.251%	$209.2932	$209.29	$209.30	$209.30
Purchase #7	$245.80	3.385%	$254.1203	$254.12	$254.10	$254.10
7 purchase totals =	$1,265.08		$1,340.9770	$1,340.98	$1,341.00	$1,341.00