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	$111.46	13.134%	$126.0992	$126.10	$126.10	$126.10
Purchase #2	$74.42	4.119%	$77.4854	$77.49	$77.50	$77.50
Purchase #3	$83.76	13.195%	$94.8121	$94.81	$94.80	$94.80
Purchase #4	$31.89	5.650%	$33.6918	$33.69	$33.70	$33.70
Purchase #5	$176.40	5.200%	$185.5728	$185.57	$185.55	$185.60
Purchase #6	$88.76	4.676%	$92.9104	$92.91	$92.90	$92.90
Purchase #7	$75.71	5.544%	$79.9074	$79.91	$79.90	$79.90
7 purchase totals =	$642.40		$690.4791	$690.48	$690.45	$690.50