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	$202.53	6.347%	$215.3846	$215.38	$215.40	$215.40
Purchase #2	$157.32	4.525%	$164.4387	$164.44	$164.45	$164.40
Purchase #3	$175.60	11.505%	$195.8028	$195.80	$195.80	$195.80
Purchase #4	$179.33	5.288%	$188.813	$188.81	$188.80	$188.80
Purchase #5	$111.77	7.619%	$120.2858	$120.29	$120.30	$120.30
Purchase #6	$40.62	4.358%	$42.3902	$42.39	$42.40	$42.40
Purchase #7	$122.72	13.872%	$139.7437	$139.74	$139.75	$139.70
7 purchase totals =	$989.89		$1,066.8588	$1,066.85	$1,066.90	$1,066.80