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	$32.86	7.871%	$35.4464	$35.45	$35.45	$35.40
Purchase #2	$197.33	12.820%	$222.6277	$222.63	$222.65	$222.60
Purchase #3	$185.41	13.116%	$209.7284	$209.73	$209.75	$209.70
Purchase #4	$29.46	12.716%	$33.2061	$33.21	$33.20	$33.20
Purchase #5	$245.73	6.857%	$262.5797	$262.58	$262.60	$262.60
Purchase #6	$212.48	6.314%	$225.896	$225.90	$225.90	$225.90
Purchase #7	$93.43	7.385%	$100.3298	$100.33	$100.35	$100.30
7 purchase totals =	$996.70		$1,089.8141	$1,089.83	$1,089.90	$1,089.70