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	$111.46	7.426%	$119.737	$119.74	$119.75	$119.70
Purchase #2	$22.87	11.604%	$25.5238	$25.52	$25.50	$25.50
Purchase #3	$184.36	6.767%	$196.8356	$196.84	$196.85	$196.80
Purchase #4	$76.98	13.543%	$87.4054	$87.41	$87.40	$87.40
Purchase #5	$180.84	13.672%	$205.5644	$205.56	$205.55	$205.60
Purchase #6	$25.72	12.359%	$28.8987	$28.90	$28.90	$28.90
Purchase #7	$93.61	12.542%	$105.3506	$105.35	$105.35	$105.40
7 purchase totals =	$695.84		$769.3155	$769.32	$769.30	$769.30