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	$168.68	10.227%	$185.9309	$185.93	$185.95	$185.90
Purchase #2	$145.41	3.214%	$150.0835	$150.08	$150.10	$150.10
Purchase #3	$54.44	13.481%	$61.7791	$61.78	$61.80	$61.80
Purchase #4	$29.46	12.772%	$33.2226	$33.22	$33.20	$33.20
Purchase #5	$165.95	12.387%	$186.5062	$186.51	$186.50	$186.50
Purchase #6	$121.25	9.213%	$132.4208	$132.42	$132.40	$132.40
Purchase #7	$49.69	3.471%	$51.4147	$51.41	$51.40	$51.40
7 purchase totals =	$734.88		$801.3578	$801.35	$801.35	$801.30