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	$203.80	7.543%	$219.1726	$219.17	$219.15	$219.20
Purchase #2	$199.60	11.376%	$222.3065	$222.31	$222.30	$222.30
Purchase #3	$240.92	7.703%	$259.4781	$259.48	$259.50	$259.50
Purchase #4	$212.52	13.299%	$240.783	$240.78	$240.80	$240.80
Purchase #5	$67.95	5.257%	$71.5221	$71.52	$71.50	$71.50
Purchase #6	$106.45	5.340%	$112.1344	$112.13	$112.15	$112.10
Purchase #7	$235.48	6.384%	$250.513	$250.51	$250.50	$250.50
7 purchase totals =	$1,266.72		$1,375.9097	$1,375.90	$1,375.90	$1,375.90