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	$130.41	10.117%	$143.6036	$143.60	$143.60	$143.60
Purchase #2	$243.32	11.299%	$270.8127	$270.81	$270.80	$270.80
Purchase #3	$49.82	13.584%	$56.5875	$56.59	$56.60	$56.60
Purchase #4	$138.46	8.853%	$150.7179	$150.72	$150.70	$150.70
Purchase #5	$154.87	5.208%	$162.9356	$162.94	$162.95	$162.90
Purchase #6	$187.56	3.749%	$194.5916	$194.59	$194.60	$194.60
Purchase #7	$44.67	8.113%	$48.2941	$48.29	$48.30	$48.30
7 purchase totals =	$949.11		$1,027.5430	$1,027.54	$1,027.55	$1,027.50