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	$127.53	3.113%	$131.5	$131.50	$131.50	$131.50
Purchase #2	$86.81	7.367%	$93.2053	$93.21	$93.20	$93.20
Purchase #3	$192.89	3.526%	$199.6913	$199.69	$199.70	$199.70
Purchase #4	$98.27	7.676%	$105.8132	$105.81	$105.80	$105.80
Purchase #5	$219.60	7.287%	$235.6023	$235.60	$235.60	$235.60
Purchase #6	$135.76	11.786%	$151.7607	$151.76	$151.75	$151.80
Purchase #7	$248.28	5.816%	$262.72	$262.72	$262.70	$262.70
7 purchase totals =	$1,109.14		$1,180.2928	$1,180.29	$1,180.25	$1,180.30