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	$154.53	10.639%	$170.9704	$170.97	$170.95	$171.00
Purchase #2	$220.44	11.810%	$246.474	$246.47	$246.45	$246.50
Purchase #3	$243.43	10.613%	$269.2652	$269.27	$269.25	$269.30
Purchase #4	$25.61	11.872%	$28.6504	$28.65	$28.65	$28.70
Purchase #5	$134.89	12.520%	$151.7782	$151.78	$151.80	$151.80
Purchase #6	$87.75	13.415%	$99.5217	$99.52	$99.50	$99.50
Purchase #7	$167.62	6.365%	$178.289	$178.29	$178.30	$178.30
7 purchase totals =	$1,034.27		$1,144.9489	$1,144.95	$1,144.90	$1,145.10