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	$60.38	12.674%	$68.0326	$68.03	$68.05	$68.00
Purchase #2	$164.84	12.842%	$186.0088	$186.01	$186.00	$186.00
Purchase #3	$53.55	11.431%	$59.6713	$59.67	$59.65	$59.70
Purchase #4	$79.37	13.210%	$89.8548	$89.85	$89.85	$89.90
Purchase #5	$228.40	9.476%	$250.0432	$250.04	$250.05	$250.00
Purchase #6	$33.33	4.625%	$34.8715	$34.87	$34.85	$34.90
Purchase #7	$5.44	10.460%	$6.009	$6.01	$6.00	$6.00
7 purchase totals =	$625.31		$694.4912	$694.48	$694.45	$694.50