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	$69.69	4.367%	$72.7334	$72.73	$72.75	$72.70
Purchase #2	$81.57	9.766%	$89.5361	$89.54	$89.55	$89.50
Purchase #3	$133.43	10.401%	$147.3081	$147.31	$147.30	$147.30
Purchase #4	$49.49	13.523%	$56.1825	$56.18	$56.20	$56.20
Purchase #5	$100.54	6.624%	$107.1998	$107.20	$107.20	$107.20
Purchase #6	$24.41	7.737%	$26.2986	$26.30	$26.30	$26.30
Purchase #7	$104.60	4.503%	$109.3101	$109.31	$109.30	$109.30
7 purchase totals =	$563.73		$608.5686	$608.57	$608.60	$608.50