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	$165.91	11.181%	$184.4604	$184.46	$184.45	$184.50
Purchase #2	$123.89	13.620%	$140.7638	$140.76	$140.75	$140.80
Purchase #3	$142.32	7.292%	$152.698	$152.70	$152.70	$152.70
Purchase #4	$136.78	10.212%	$150.748	$150.75	$150.75	$150.70
Purchase #5	$155.65	10.379%	$171.8049	$171.80	$171.80	$171.80
Purchase #6	$206.82	4.773%	$216.6915	$216.69	$216.70	$216.70
Purchase #7	$43.44	8.406%	$47.0916	$47.09	$47.10	$47.10
7 purchase totals =	$974.81		$1,064.2582	$1,064.25	$1,064.25	$1,064.30