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	$135.34	11.618%	$151.0638	$151.06	$151.05	$151.10
Purchase #2	$153.76	7.282%	$164.9568	$164.96	$164.95	$165.00
Purchase #3	$145.31	9.148%	$158.603	$158.60	$158.60	$158.60
Purchase #4	$166.65	3.418%	$172.3461	$172.35	$172.35	$172.30
Purchase #5	$34.83	12.529%	$39.1939	$39.19	$39.20	$39.20
Purchase #6	$217.56	3.607%	$225.4074	$225.41	$225.40	$225.40
Purchase #7	$143.83	11.824%	$160.8365	$160.84	$160.85	$160.80
7 purchase totals =	$997.28		$1,072.4075	$1,072.41	$1,072.40	$1,072.40