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	$160.78	6.465%	$171.1744	$171.17	$171.15	$171.20
Purchase #2	$89.69	7.250%	$96.1925	$96.19	$96.20	$96.20
Purchase #3	$13.55	7.422%	$14.5557	$14.56	$14.55	$14.60
Purchase #4	$221.75	10.305%	$244.6013	$244.60	$244.60	$244.60
Purchase #5	$178.77	7.272%	$191.7702	$191.77	$191.75	$191.80
Purchase #6	$132.27	9.517%	$144.8581	$144.86	$144.85	$144.90
Purchase #7	$129.26	6.229%	$137.3116	$137.31	$137.30	$137.30
7 purchase totals =	$926.07		$1,000.4638	$1,000.46	$1,000.40	$1,000.60