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	$101.53	5.292%	$106.903	$106.90	$106.90	$106.90
Purchase #2	$40.71	8.870%	$44.321	$44.32	$44.30	$44.30
Purchase #3	$164.72	11.291%	$183.3185	$183.32	$183.30	$183.30
Purchase #4	$206.47	5.660%	$218.1562	$218.16	$218.15	$218.20
Purchase #5	$26.31	6.820%	$28.1043	$28.10	$28.10	$28.10
Purchase #6	$160.37	4.651%	$167.8288	$167.83	$167.85	$167.80
Purchase #7	$47.82	9.848%	$52.5293	$52.53	$52.55	$52.50
7 purchase totals =	$747.93		$801.1611	$801.16	$801.15	$801.10