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	$145.55	4.526%	$152.1376	$152.14	$152.15	$152.10
Purchase #2	$164.77	10.540%	$182.1368	$182.14	$182.15	$182.10
Purchase #3	$39.71	11.756%	$44.3783	$44.38	$44.40	$44.40
Purchase #4	$96.42	7.276%	$103.4355	$103.44	$103.45	$103.40
Purchase #5	$221.58	10.220%	$244.2255	$244.23	$244.25	$244.20
Purchase #6	$138.62	7.852%	$149.5044	$149.50	$149.50	$149.50
Purchase #7	$117.28	8.558%	$127.3168	$127.32	$127.30	$127.30
7 purchase totals =	$923.93		$1,003.1349	$1,003.15	$1,003.20	$1,003.00