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	$111.60	4.612%	$116.747	$116.75	$116.75	$116.70
Purchase #2	$250.56	7.460%	$269.2518	$269.25	$269.25	$269.30
Purchase #3	$219.67	4.218%	$228.9357	$228.94	$228.95	$228.90
Purchase #4	$105.42	13.128%	$119.2595	$119.26	$119.25	$119.30
Purchase #5	$157.52	11.484%	$175.6096	$175.61	$175.60	$175.60
Purchase #6	$247.41	11.268%	$275.2882	$275.29	$275.30	$275.30
Purchase #7	$80.37	3.126%	$82.8824	$82.88	$82.90	$82.90
7 purchase totals =	$1,172.55		$1,267.9742	$1,267.98	$1,268.00	$1,268.00