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	$35.73	5.184%	$37.5822	$37.58	$37.60	$37.60
Purchase #2	$46.31	5.581%	$48.8946	$48.89	$48.90	$48.90
Purchase #3	$40.92	11.774%	$45.7379	$45.74	$45.75	$45.70
Purchase #4	$174.41	4.172%	$181.6864	$181.69	$181.70	$181.70
Purchase #5	$185.63	3.391%	$191.9247	$191.92	$191.90	$191.90
Purchase #6	$170.86	10.718%	$189.1728	$189.17	$189.15	$189.20
Purchase #7	$19.40	5.723%	$20.5103	$20.51	$20.50	$20.50
7 purchase totals =	$673.26		$715.5089	$715.50	$715.50	$715.50