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	$117.96	13.492%	$133.8752	$133.88	$133.90	$133.90
Purchase #2	$43.31	5.154%	$45.5422	$45.54	$45.55	$45.50
Purchase #3	$208.34	6.830%	$222.5696	$222.57	$222.55	$222.60
Purchase #4	$103.26	8.567%	$112.1063	$112.11	$112.10	$112.10
Purchase #5	$81.56	13.503%	$92.573	$92.57	$92.55	$92.60
Purchase #6	$129.69	3.528%	$134.2655	$134.27	$134.25	$134.30
Purchase #7	$248.48	13.214%	$281.3141	$281.31	$281.30	$281.30
7 purchase totals =	$932.60		$1,022.2459	$1,022.25	$1,022.20	$1,022.30