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	$42.62	7.410%	$45.7781	$45.78	$45.80	$45.80
Purchase #2	$40.61	12.750%	$45.7878	$45.79	$45.80	$45.80
Purchase #3	$246.46	12.482%	$277.2231	$277.22	$277.20	$277.20
Purchase #4	$190.89	10.233%	$210.4238	$210.42	$210.40	$210.40
Purchase #5	$220.28	11.155%	$244.8522	$244.85	$244.85	$244.90
Purchase #6	$99.28	12.343%	$111.5341	$111.53	$111.55	$111.50
Purchase #7	$106.58	11.116%	$118.4274	$118.43	$118.45	$118.40
7 purchase totals =	$946.72		$1,054.0265	$1,054.02	$1,054.05	$1,054.00