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	$133.55	13.848%	$152.044	$152.04	$152.05	$152.00
Purchase #2	$117.92	11.501%	$131.482	$131.48	$131.50	$131.50
Purchase #3	$140.72	7.449%	$151.2022	$151.20	$151.20	$151.20
Purchase #4	$65.37	3.705%	$67.792	$67.79	$67.80	$67.80
Purchase #5	$35.38	6.285%	$37.6036	$37.60	$37.60	$37.60
Purchase #6	$48.47	3.841%	$50.3317	$50.33	$50.35	$50.30
Purchase #7	$5.90	8.397%	$6.3954	$6.40	$6.40	$6.40
7 purchase totals =	$547.31		$596.8509	$596.84	$596.90	$596.80