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	$42.88	5.707%	$45.3272	$45.33	$45.35	$45.30
Purchase #2	$77.44	7.660%	$83.3719	$83.37	$83.35	$83.40
Purchase #3	$134.53	9.422%	$147.2054	$147.21	$147.20	$147.20
Purchase #4	$222.77	8.354%	$241.3802	$241.38	$241.40	$241.40
Purchase #5	$142.69	9.601%	$156.3897	$156.39	$156.40	$156.40
Purchase #6	$140.38	5.852%	$148.595	$148.60	$148.60	$148.60
Purchase #7	$98.68	3.141%	$101.7795	$101.78	$101.80	$101.80
7 purchase totals =	$859.37		$924.0489	$924.06	$924.10	$924.10