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	$171.61	5.753%	$181.4827	$181.48	$181.50	$181.50
Purchase #2	$139.91	7.495%	$150.3963	$150.40	$150.40	$150.40
Purchase #3	$77.29	4.230%	$80.5594	$80.56	$80.55	$80.60
Purchase #4	$45.88	6.809%	$49.004	$49.00	$49.00	$49.00
Purchase #5	$146.95	9.825%	$161.3878	$161.39	$161.40	$161.40
Purchase #6	$180.89	5.444%	$190.7377	$190.74	$190.75	$190.70
Purchase #7	$180.28	6.166%	$191.3961	$191.40	$191.40	$191.40
7 purchase totals =	$942.81		$1,004.9640	$1,004.97	$1,005.00	$1,005.00