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	$188.84	10.858%	$209.3442	$209.34	$209.35	$209.30
Purchase #2	$159.52	6.871%	$170.4806	$170.48	$170.50	$170.50
Purchase #3	$28.71	9.407%	$31.4107	$31.41	$31.40	$31.40
Purchase #4	$190.71	7.241%	$204.5193	$204.52	$204.50	$204.50
Purchase #5	$106.76	4.180%	$111.2226	$111.22	$111.20	$111.20
Purchase #6	$177.43	11.805%	$198.3756	$198.38	$198.40	$198.40
Purchase #7	$86.26	10.386%	$95.219	$95.22	$95.20	$95.20
7 purchase totals =	$938.23		$1,020.5720	$1,020.57	$1,020.55	$1,020.50