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	$216.96	10.188%	$239.0639	$239.06	$239.05	$239.10
Purchase #2	$52.98	10.285%	$58.429	$58.43	$58.45	$58.40
Purchase #3	$223.31	6.849%	$238.6045	$238.60	$238.60	$238.60
Purchase #4	$128.27	10.136%	$141.2714	$141.27	$141.25	$141.30
Purchase #5	$152.34	5.197%	$160.2571	$160.26	$160.25	$160.30
Purchase #6	$239.87	11.685%	$267.8988	$267.90	$267.90	$267.90
Purchase #7	$76.28	5.392%	$80.393	$80.39	$80.40	$80.40
7 purchase totals =	$1,090.01		$1,185.9177	$1,185.91	$1,185.90	$1,186.00