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	$170.95	12.724%	$192.7017	$192.70	$192.70	$192.70
Purchase #2	$196.40	9.117%	$214.3058	$214.31	$214.30	$214.30
Purchase #3	$226.88	7.186%	$243.1836	$243.18	$243.20	$243.20
Purchase #4	$99.57	11.688%	$111.2077	$111.21	$111.20	$111.20
Purchase #5	$64.87	4.526%	$67.806	$67.81	$67.80	$67.80
Purchase #6	$174.88	9.475%	$191.4499	$191.45	$191.45	$191.40
Purchase #7	$158.76	3.782%	$164.7643	$164.76	$164.75	$164.80
7 purchase totals =	$1,092.31		$1,185.4190	$1,185.42	$1,185.40	$1,185.40