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	$75.55	9.697%	$82.8761	$82.88	$82.90	$82.90
Purchase #2	$11.73	7.483%	$12.6078	$12.61	$12.60	$12.60
Purchase #3	$139.92	11.113%	$155.4693	$155.47	$155.45	$155.50
Purchase #4	$191.52	10.414%	$211.4649	$211.46	$211.45	$211.50
Purchase #5	$55.45	3.288%	$57.2732	$57.27	$57.25	$57.30
Purchase #6	$208.31	8.361%	$225.7268	$225.73	$225.75	$225.70
Purchase #7	$23.81	8.731%	$25.8889	$25.89	$25.90	$25.90
7 purchase totals =	$706.29		$771.3070	$771.31	$771.30	$771.40