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	$58.61	6.180%	$62.2321	$62.23	$62.25	$62.20
Purchase #2	$55.77	10.661%	$61.7156	$61.72	$61.70	$61.70
Purchase #3	$123.70	12.391%	$139.0277	$139.03	$139.05	$139.00
Purchase #4	$149.41	12.384%	$167.9129	$167.91	$167.90	$167.90
Purchase #5	$235.38	10.778%	$260.7493	$260.75	$260.75	$260.70
Purchase #6	$244.89	11.483%	$273.0107	$273.01	$273.00	$273.00
Purchase #7	$142.35	4.159%	$148.2703	$148.27	$148.25	$148.30
7 purchase totals =	$1,010.11		$1,112.9186	$1,112.92	$1,112.90	$1,112.80