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	$9.67	4.641%	$10.1188	$10.12	$10.10	$10.10
Purchase #2	$48.43	10.692%	$53.6081	$53.61	$53.60	$53.60
Purchase #3	$219.80	3.751%	$228.0447	$228.04	$228.05	$228.00
Purchase #4	$178.40	3.791%	$185.1631	$185.16	$185.15	$185.20
Purchase #5	$78.30	8.401%	$84.878	$84.88	$84.90	$84.90
Purchase #6	$250.68	10.228%	$276.3196	$276.32	$276.30	$276.30
Purchase #7	$129.61	10.693%	$143.4692	$143.47	$143.45	$143.50
7 purchase totals =	$914.89		$981.6015	$981.60	$981.55	$981.60