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	$191.80	11.253%	$213.3833	$213.38	$213.40	$213.40
Purchase #2	$98.25	3.525%	$101.7133	$101.71	$101.70	$101.70
Purchase #3	$50.72	3.485%	$52.4876	$52.49	$52.50	$52.50
Purchase #4	$165.31	4.528%	$172.7952	$172.80	$172.80	$172.80
Purchase #5	$131.26	13.431%	$148.8895	$148.89	$148.90	$148.90
Purchase #6	$166.25	3.745%	$172.4761	$172.48	$172.50	$172.50
Purchase #7	$91.76	4.790%	$96.1553	$96.16	$96.15	$96.20
7 purchase totals =	$895.35		$957.9003	$957.91	$957.95	$958.00