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	$195.29	10.157%	$215.1256	$215.13	$215.15	$215.10
Purchase #2	$120.30	13.324%	$136.3288	$136.33	$136.35	$136.30
Purchase #3	$100.96	13.538%	$114.628	$114.63	$114.65	$114.60
Purchase #4	$24.50	3.369%	$25.3254	$25.33	$25.35	$25.30
Purchase #5	$97.71	3.254%	$100.8895	$100.89	$100.90	$100.90
Purchase #6	$125.48	6.871%	$134.1017	$134.10	$134.10	$134.10
Purchase #7	$99.59	8.867%	$108.4206	$108.42	$108.40	$108.40
7 purchase totals =	$763.83		$834.8196	$834.83	$834.90	$834.70