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	$125.43	11.239%	$139.5271	$139.53	$139.55	$139.50
Purchase #2	$169.38	12.550%	$190.6372	$190.64	$190.65	$190.60
Purchase #3	$132.59	12.620%	$149.3229	$149.32	$149.30	$149.30
Purchase #4	$83.42	13.332%	$94.5416	$94.54	$94.55	$94.50
Purchase #5	$127.99	11.802%	$143.0954	$143.10	$143.10	$143.10
Purchase #6	$49.91	12.556%	$56.1767	$56.18	$56.20	$56.20
Purchase #7	$223.51	7.616%	$240.5325	$240.53	$240.55	$240.50
7 purchase totals =	$912.23		$1,013.8334	$1,013.84	$1,013.90	$1,013.70