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	$131.72	11.127%	$146.3765	$146.38	$146.40	$146.40
Purchase #2	$65.58	9.168%	$71.5924	$71.59	$71.60	$71.60
Purchase #3	$150.33	6.592%	$160.2398	$160.24	$160.25	$160.20
Purchase #4	$171.63	11.239%	$190.9195	$190.92	$190.90	$190.90
Purchase #5	$234.97	6.647%	$250.5885	$250.59	$250.60	$250.60
Purchase #6	$222.77	8.460%	$241.6163	$241.62	$241.60	$241.60
Purchase #7	$46.95	7.747%	$50.5872	$50.59	$50.60	$50.60
7 purchase totals =	$1,023.95		$1,111.9202	$1,111.93	$1,111.95	$1,111.90