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	$185.60	5.830%	$196.4205	$196.42	$196.40	$196.40
Purchase #2	$72.92	5.489%	$76.9226	$76.92	$76.90	$76.90
Purchase #3	$47.67	7.292%	$51.1461	$51.15	$51.15	$51.10
Purchase #4	$190.29	4.525%	$198.9006	$198.90	$198.90	$198.90
Purchase #5	$21.60	3.741%	$22.4081	$22.41	$22.40	$22.40
Purchase #6	$241.70	10.134%	$266.1939	$266.19	$266.20	$266.20
Purchase #7	$99.73	4.718%	$104.4353	$104.44	$104.45	$104.40
7 purchase totals =	$859.51		$916.4271	$916.43	$916.40	$916.30