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	$147.66	6.563%	$157.3509	$157.35	$157.35	$157.40
Purchase #2	$47.91	12.176%	$53.7435	$53.74	$53.75	$53.70
Purchase #3	$240.49	10.153%	$264.9069	$264.91	$264.90	$264.90
Purchase #4	$64.37	10.779%	$71.3084	$71.31	$71.30	$71.30
Purchase #5	$19.86	4.446%	$20.743	$20.74	$20.75	$20.70
Purchase #6	$89.31	7.530%	$96.035	$96.04	$96.05	$96.00
Purchase #7	$18.50	11.750%	$20.6738	$20.67	$20.65	$20.70
7 purchase totals =	$628.10		$684.7615	$684.76	$684.75	$684.70