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	$85.78	7.201%	$91.957	$91.96	$91.95	$92.00
Purchase #2	$191.83	12.346%	$215.5133	$215.51	$215.50	$215.50
Purchase #3	$169.38	9.295%	$185.1239	$185.12	$185.10	$185.10
Purchase #4	$75.25	4.214%	$78.421	$78.42	$78.40	$78.40
Purchase #5	$124.35	13.611%	$141.2753	$141.28	$141.30	$141.30
Purchase #6	$199.58	9.590%	$218.7197	$218.72	$218.70	$218.70
Purchase #7	$127.81	12.345%	$143.5881	$143.59	$143.60	$143.60
7 purchase totals =	$973.98		$1,074.5983	$1,074.60	$1,074.55	$1,074.60