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	$193.48	8.626%	$210.1696	$210.17	$210.15	$210.20
Purchase #2	$115.85	12.327%	$130.1308	$130.13	$130.15	$130.10
Purchase #3	$245.61	8.136%	$265.5928	$265.59	$265.60	$265.60
Purchase #4	$70.91	10.367%	$78.2612	$78.26	$78.25	$78.30
Purchase #5	$204.59	13.761%	$232.7436	$232.74	$232.75	$232.70
Purchase #6	$29.91	9.714%	$32.8155	$32.82	$32.80	$32.80
Purchase #7	$145.31	11.316%	$161.7533	$161.75	$161.75	$161.80
7 purchase totals =	$1,005.66		$1,111.4668	$1,111.46	$1,111.45	$1,111.50