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	$87.25	11.727%	$97.4818	$97.48	$97.50	$97.50
Purchase #2	$243.28	7.486%	$261.4919	$261.49	$261.50	$261.50
Purchase #3	$46.89	13.560%	$53.2483	$53.25	$53.25	$53.20
Purchase #4	$51.72	3.368%	$53.4619	$53.46	$53.45	$53.50
Purchase #5	$167.54	12.836%	$189.0454	$189.05	$189.05	$189.00
Purchase #6	$195.30	3.342%	$201.8269	$201.83	$201.85	$201.80
Purchase #7	$199.74	8.143%	$216.0048	$216.00	$216.00	$216.00
7 purchase totals =	$991.72		$1,072.5610	$1,072.56	$1,072.60	$1,072.50