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	$62.57	7.806%	$67.4542	$67.45	$67.45	$67.50
Purchase #2	$84.42	6.379%	$89.8052	$89.81	$89.80	$89.80
Purchase #3	$85.45	3.363%	$88.3237	$88.32	$88.30	$88.30
Purchase #4	$246.87	11.458%	$275.1564	$275.16	$275.15	$275.20
Purchase #5	$28.84	8.234%	$31.2147	$31.21	$31.20	$31.20
Purchase #6	$171.83	7.528%	$184.7654	$184.77	$184.75	$184.80
Purchase #7	$45.76	9.771%	$50.2312	$50.23	$50.25	$50.20
7 purchase totals =	$725.74		$786.9508	$786.95	$786.90	$787.00