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	$166.28	11.539%	$185.467	$185.47	$185.45	$185.50
Purchase #2	$128.66	8.707%	$139.8624	$139.86	$139.85	$139.90
Purchase #3	$38.28	11.340%	$42.621	$42.62	$42.60	$42.60
Purchase #4	$168.59	13.733%	$191.7425	$191.74	$191.75	$191.70
Purchase #5	$31.29	11.851%	$34.9982	$35.00	$35.00	$35.00
Purchase #6	$52.90	5.492%	$55.8053	$55.81	$55.80	$55.80
Purchase #7	$75.76	9.302%	$82.8072	$82.81	$82.80	$82.80
7 purchase totals =	$661.76		$733.3036	$733.31	$733.25	$733.30