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	$161.59	6.803%	$172.583	$172.58	$172.60	$172.60
Purchase #2	$193.55	8.745%	$210.4759	$210.48	$210.50	$210.50
Purchase #3	$30.29	13.394%	$34.347	$34.35	$34.35	$34.30
Purchase #4	$54.48	8.654%	$59.1947	$59.19	$59.20	$59.20
Purchase #5	$31.38	13.301%	$35.5539	$35.55	$35.55	$35.60
Purchase #6	$219.73	11.640%	$245.3066	$245.31	$245.30	$245.30
Purchase #7	$210.45	4.505%	$219.9308	$219.93	$219.95	$219.90
7 purchase totals =	$901.47		$977.3919	$977.39	$977.45	$977.40