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	$65.62	8.244%	$71.0297	$71.03	$71.05	$71.00
Purchase #2	$85.51	6.217%	$90.8262	$90.83	$90.85	$90.80
Purchase #3	$168.69	11.407%	$187.9325	$187.93	$187.95	$187.90
Purchase #4	$47.48	12.644%	$53.4834	$53.48	$53.50	$53.50
Purchase #5	$106.60	7.761%	$114.8732	$114.87	$114.85	$114.90
Purchase #6	$55.50	8.111%	$60.0016	$60.00	$60.00	$60.00
Purchase #7	$190.77	8.755%	$207.4719	$207.47	$207.45	$207.50
7 purchase totals =	$720.17		$785.6185	$785.61	$785.65	$785.60