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	$179.60	8.209%	$194.3434	$194.34	$194.35	$194.30
Purchase #2	$123.78	10.465%	$136.7336	$136.73	$136.75	$136.70
Purchase #3	$210.94	9.212%	$230.3718	$230.37	$230.35	$230.40
Purchase #4	$56.47	5.240%	$59.429	$59.43	$59.45	$59.40
Purchase #5	$24.53	4.112%	$25.5387	$25.54	$25.55	$25.50
Purchase #6	$87.26	4.390%	$91.0907	$91.09	$91.10	$91.10
Purchase #7	$52.89	4.754%	$55.4044	$55.40	$55.40	$55.40
7 purchase totals =	$735.47		$792.9116	$792.90	$792.95	$792.80