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	$193.52	11.874%	$216.4986	$216.50	$216.50	$216.50
Purchase #2	$221.89	9.251%	$242.417	$242.42	$242.40	$242.40
Purchase #3	$215.54	7.334%	$231.3477	$231.35	$231.35	$231.30
Purchase #4	$41.88	8.867%	$45.5935	$45.59	$45.60	$45.60
Purchase #5	$30.52	4.242%	$31.8147	$31.81	$31.80	$31.80
Purchase #6	$129.51	8.494%	$140.5106	$140.51	$140.50	$140.50
Purchase #7	$225.81	7.476%	$242.6916	$242.69	$242.70	$242.70
7 purchase totals =	$1,058.67		$1,150.8737	$1,150.87	$1,150.85	$1,150.80