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	$136.80	9.119%	$149.2748	$149.27	$149.25	$149.30
Purchase #2	$75.77	3.311%	$78.2787	$78.28	$78.30	$78.30
Purchase #3	$27.56	5.365%	$29.0386	$29.04	$29.05	$29.00
Purchase #4	$33.38	11.571%	$37.2424	$37.24	$37.25	$37.20
Purchase #5	$149.59	7.190%	$160.3455	$160.35	$160.35	$160.30
Purchase #6	$152.91	7.320%	$164.103	$164.10	$164.10	$164.10
Purchase #7	$147.38	13.539%	$167.3338	$167.33	$167.35	$167.30
7 purchase totals =	$723.39		$785.6168	$785.61	$785.65	$785.50