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	$124.29	12.769%	$140.1606	$140.16	$140.15	$140.20
Purchase #2	$237.80	6.861%	$254.1155	$254.12	$254.10	$254.10
Purchase #3	$198.30	12.285%	$222.6612	$222.66	$222.65	$222.70
Purchase #4	$157.38	5.402%	$165.8817	$165.88	$165.90	$165.90
Purchase #5	$101.69	6.481%	$108.2805	$108.28	$108.30	$108.30
Purchase #6	$125.96	5.440%	$132.8122	$132.81	$132.80	$132.80
Purchase #7	$166.48	6.251%	$176.8867	$176.89	$176.90	$176.90
7 purchase totals =	$1,111.90		$1,200.7984	$1,200.80	$1,200.80	$1,200.90