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	$64.48	4.793%	$67.5705	$67.57	$67.55	$67.60
Purchase #2	$229.67	4.133%	$239.1623	$239.16	$239.15	$239.20
Purchase #3	$74.26	5.156%	$78.0888	$78.09	$78.10	$78.10
Purchase #4	$250.25	12.478%	$281.4762	$281.48	$281.50	$281.50
Purchase #5	$34.54	9.185%	$37.7125	$37.71	$37.70	$37.70
Purchase #6	$172.50	10.423%	$190.4797	$190.48	$190.50	$190.50
Purchase #7	$222.46	9.376%	$243.3178	$243.32	$243.30	$243.30
7 purchase totals =	$1,048.16		$1,137.8078	$1,137.81	$1,137.80	$1,137.90