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	$134.39	11.321%	$149.6043	$149.60	$149.60	$149.60
Purchase #2	$113.60	3.775%	$117.8884	$117.89	$117.90	$117.90
Purchase #3	$56.83	5.330%	$59.859	$59.86	$59.85	$59.90
Purchase #4	$211.95	8.198%	$229.3257	$229.33	$229.35	$229.30
Purchase #5	$73.33	5.357%	$77.2583	$77.26	$77.25	$77.30
Purchase #6	$202.52	4.859%	$212.3604	$212.36	$212.35	$212.40
Purchase #7	$235.25	12.773%	$265.2985	$265.30	$265.30	$265.30
7 purchase totals =	$1,027.87		$1,111.5946	$1,111.60	$1,111.60	$1,111.70