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	$77.52	10.482%	$85.6456	$85.65	$85.65	$85.60
Purchase #2	$222.46	5.314%	$234.2815	$234.28	$234.30	$234.30
Purchase #3	$248.54	13.203%	$281.3547	$281.35	$281.35	$281.40
Purchase #4	$66.50	13.695%	$75.6072	$75.61	$75.60	$75.60
Purchase #5	$93.31	8.699%	$101.427	$101.43	$101.45	$101.40
Purchase #6	$168.94	9.679%	$185.2917	$185.29	$185.30	$185.30
Purchase #7	$174.62	7.619%	$187.9243	$187.92	$187.90	$187.90
7 purchase totals =	$1,051.89		$1,151.5320	$1,151.53	$1,151.55	$1,151.50