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	$70.49	4.313%	$73.5302	$73.53	$73.55	$73.50
Purchase #2	$223.76	4.299%	$233.3794	$233.38	$233.40	$233.40
Purchase #3	$88.58	13.644%	$100.6659	$100.67	$100.65	$100.70
Purchase #4	$160.59	4.433%	$167.709	$167.71	$167.70	$167.70
Purchase #5	$41.26	3.788%	$42.8229	$42.82	$42.80	$42.80
Purchase #6	$213.66	12.463%	$240.2884	$240.29	$240.30	$240.30
Purchase #7	$102.93	4.427%	$107.4867	$107.49	$107.50	$107.50
7 purchase totals =	$901.27		$965.8825	$965.89	$965.90	$965.90