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	$189.55	3.726%	$196.6126	$196.61	$196.60	$196.60
Purchase #2	$234.29	10.297%	$258.4148	$258.41	$258.40	$258.40
Purchase #3	$14.33	13.549%	$16.2716	$16.27	$16.25	$16.30
Purchase #4	$217.99	8.345%	$236.1813	$236.18	$236.20	$236.20
Purchase #5	$92.73	7.658%	$99.8313	$99.83	$99.85	$99.80
Purchase #6	$204.83	5.406%	$215.9031	$215.90	$215.90	$215.90
Purchase #7	$233.66	9.867%	$256.7152	$256.72	$256.70	$256.70
7 purchase totals =	$1,187.38		$1,279.9299	$1,279.92	$1,279.90	$1,279.90