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	$193.91	13.827%	$220.7219	$220.72	$220.70	$220.70
Purchase #2	$59.76	9.138%	$65.2209	$65.22	$65.20	$65.20
Purchase #3	$216.72	13.232%	$245.3964	$245.40	$245.40	$245.40
Purchase #4	$18.87	10.141%	$20.7836	$20.78	$20.80	$20.80
Purchase #5	$164.57	11.717%	$183.8527	$183.85	$183.85	$183.90
Purchase #6	$89.78	10.346%	$99.0686	$99.07	$99.05	$99.10
Purchase #7	$232.53	6.462%	$247.5561	$247.56	$247.55	$247.60
7 purchase totals =	$976.14		$1,082.6002	$1,082.60	$1,082.55	$1,082.70