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	$214.40	10.484%	$236.8777	$236.88	$236.90	$236.90
Purchase #2	$197.59	12.681%	$222.6464	$222.65	$222.65	$222.60
Purchase #3	$117.41	12.223%	$131.761	$131.76	$131.75	$131.80
Purchase #4	$153.86	8.626%	$167.132	$167.13	$167.15	$167.10
Purchase #5	$104.78	11.511%	$116.8412	$116.84	$116.85	$116.80
Purchase #6	$91.85	8.540%	$99.694	$99.69	$99.70	$99.70
Purchase #7	$190.87	11.418%	$212.6635	$212.66	$212.65	$212.70
7 purchase totals =	$1,070.76		$1,187.6158	$1,187.61	$1,187.65	$1,187.60