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	$141.66	3.350%	$146.4056	$146.41	$146.40	$146.40
Purchase #2	$221.46	10.116%	$243.8629	$243.86	$243.85	$243.90
Purchase #3	$24.29	13.438%	$27.5541	$27.55	$27.55	$27.60
Purchase #4	$39.85	9.106%	$43.4787	$43.48	$43.50	$43.50
Purchase #5	$147.63	13.735%	$167.907	$167.91	$167.90	$167.90
Purchase #6	$88.76	8.826%	$96.594	$96.59	$96.60	$96.60
Purchase #7	$11.31	8.773%	$12.3022	$12.30	$12.30	$12.30
7 purchase totals =	$674.96		$738.1045	$738.10	$738.10	$738.20