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	$222.30	11.111%	$246.9998	$247.00	$247.00	$247.00
Purchase #2	$143.55	11.723%	$160.3784	$160.38	$160.40	$160.40
Purchase #3	$96.74	11.174%	$107.5497	$107.55	$107.55	$107.50
Purchase #4	$99.60	12.144%	$111.6954	$111.70	$111.70	$111.70
Purchase #5	$119.42	3.272%	$123.3274	$123.33	$123.35	$123.30
Purchase #6	$12.67	6.459%	$13.4884	$13.49	$13.50	$13.50
Purchase #7	$30.44	7.871%	$32.8359	$32.84	$32.85	$32.80
7 purchase totals =	$724.72		$796.2750	$796.29	$796.35	$796.20