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	$42.45	6.234%	$45.0963	$45.10	$45.10	$45.10
Purchase #2	$35.34	7.374%	$37.946	$37.95	$37.95	$37.90
Purchase #3	$146.81	3.371%	$151.759	$151.76	$151.75	$151.80
Purchase #4	$30.97	4.621%	$32.4011	$32.40	$32.40	$32.40
Purchase #5	$62.61	13.328%	$70.9547	$70.95	$70.95	$71.00
Purchase #6	$31.98	10.178%	$35.2349	$35.23	$35.25	$35.20
Purchase #7	$18.94	7.527%	$20.3656	$20.37	$20.35	$20.40
7 purchase totals =	$369.10		$393.7576	$393.76	$393.75	$393.80