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	$66.64	7.167%	$71.4161	$71.42	$71.40	$71.40
Purchase #2	$159.89	5.149%	$168.1227	$168.12	$168.10	$168.10
Purchase #3	$64.94	6.244%	$68.9949	$68.99	$69.00	$69.00
Purchase #4	$64.73	8.782%	$70.4146	$70.41	$70.40	$70.40
Purchase #5	$139.87	7.561%	$150.4456	$150.45	$150.45	$150.40
Purchase #6	$41.25	3.833%	$42.8311	$42.83	$42.85	$42.80
Purchase #7	$110.81	6.237%	$117.7212	$117.72	$117.70	$117.70
7 purchase totals =	$648.13		$689.9462	$689.94	$689.90	$689.80