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	$63.48	10.172%	$69.9372	$69.94	$69.95	$69.90
Purchase #2	$41.58	10.288%	$45.8578	$45.86	$45.85	$45.90
Purchase #3	$231.50	10.584%	$256.002	$256.00	$256.00	$256.00
Purchase #4	$50.38	8.607%	$54.7162	$54.72	$54.70	$54.70
Purchase #5	$228.52	13.470%	$259.3016	$259.30	$259.30	$259.30
Purchase #6	$202.43	10.596%	$223.8795	$223.88	$223.90	$223.90
Purchase #7	$18.70	5.516%	$19.7315	$19.73	$19.75	$19.70
7 purchase totals =	$836.59		$929.4258	$929.43	$929.45	$929.40