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	$165.96	13.364%	$188.1389	$188.14	$188.15	$188.10
Purchase #2	$127.82	11.252%	$142.2023	$142.20	$142.20	$142.20
Purchase #3	$205.78	5.229%	$216.5402	$216.54	$216.55	$216.50
Purchase #4	$155.61	12.181%	$174.5649	$174.56	$174.55	$174.60
Purchase #5	$114.31	8.363%	$123.8697	$123.87	$123.85	$123.90
Purchase #6	$114.81	3.603%	$118.9466	$118.95	$118.95	$118.90
Purchase #7	$213.54	3.863%	$221.7891	$221.79	$221.80	$221.80
7 purchase totals =	$1,097.83		$1,186.0517	$1,186.05	$1,186.05	$1,186.00