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	$128.48	3.160%	$132.54	$132.54	$132.55	$132.50
Purchase #2	$90.91	4.306%	$94.8246	$94.82	$94.80	$94.80
Purchase #3	$135.27	12.274%	$151.873	$151.87	$151.85	$151.90
Purchase #4	$19.56	13.393%	$22.1797	$22.18	$22.20	$22.20
Purchase #5	$155.48	8.274%	$168.3444	$168.34	$168.35	$168.30
Purchase #6	$174.72	13.392%	$198.1185	$198.12	$198.10	$198.10
Purchase #7	$140.85	11.342%	$156.8252	$156.83	$156.85	$156.80
7 purchase totals =	$845.27		$924.7054	$924.70	$924.70	$924.60