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	$115.72	12.195%	$129.8321	$129.83	$129.85	$129.80
Purchase #2	$223.98	8.457%	$242.922	$242.92	$242.90	$242.90
Purchase #3	$19.82	7.486%	$21.3037	$21.30	$21.30	$21.30
Purchase #4	$139.71	8.819%	$152.031	$152.03	$152.05	$152.00
Purchase #5	$191.49	9.406%	$209.5015	$209.50	$209.50	$209.50
Purchase #6	$159.80	3.821%	$165.906	$165.91	$165.90	$165.90
Purchase #7	$204.72	9.149%	$223.4498	$223.45	$223.45	$223.40
7 purchase totals =	$1,055.24		$1,144.9461	$1,144.94	$1,144.95	$1,144.80