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	$151.96	12.673%	$171.2179	$171.22	$171.20	$171.20
Purchase #2	$90.55	10.249%	$99.8305	$99.83	$99.85	$99.80
Purchase #3	$190.84	4.746%	$199.8973	$199.90	$199.90	$199.90
Purchase #4	$208.86	4.521%	$218.3026	$218.30	$218.30	$218.30
Purchase #5	$170.37	11.196%	$189.4446	$189.44	$189.45	$189.40
Purchase #6	$107.57	3.170%	$110.98	$110.98	$111.00	$111.00
Purchase #7	$41.38	8.172%	$44.7616	$44.76	$44.75	$44.80
7 purchase totals =	$961.53		$1,034.4345	$1,034.43	$1,034.45	$1,034.40