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	$198.98	7.627%	$214.1562	$214.16	$214.15	$214.20
Purchase #2	$248.91	12.733%	$280.6037	$280.60	$280.60	$280.60
Purchase #3	$250.63	13.446%	$284.3297	$284.33	$284.35	$284.30
Purchase #4	$57.73	5.404%	$60.8497	$60.85	$60.85	$60.80
Purchase #5	$177.29	5.614%	$187.2431	$187.24	$187.25	$187.20
Purchase #6	$169.40	7.121%	$181.463	$181.46	$181.45	$181.50
Purchase #7	$154.91	10.802%	$171.6434	$171.64	$171.65	$171.60
7 purchase totals =	$1,257.85		$1,380.2888	$1,380.28	$1,380.30	$1,380.20