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	$42.57	5.750%	$45.0178	$45.02	$45.00	$45.00
Purchase #2	$180.94	7.628%	$194.7421	$194.74	$194.75	$194.70
Purchase #3	$209.99	11.392%	$233.9121	$233.91	$233.90	$233.90
Purchase #4	$156.57	4.790%	$164.0697	$164.07	$164.05	$164.10
Purchase #5	$43.83	13.462%	$49.7304	$49.73	$49.75	$49.70
Purchase #6	$89.34	3.774%	$92.7117	$92.71	$92.70	$92.70
Purchase #7	$196.95	13.142%	$222.8332	$222.83	$222.85	$222.80
7 purchase totals =	$920.19		$1,003.0170	$1,003.01	$1,003.00	$1,002.90