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	$149.66	5.295%	$157.5845	$157.58	$157.60	$157.60
Purchase #2	$33.71	11.501%	$37.587	$37.59	$37.60	$37.60
Purchase #3	$50.82	8.710%	$55.2464	$55.25	$55.25	$55.20
Purchase #4	$240.76	13.719%	$273.7899	$273.79	$273.80	$273.80
Purchase #5	$70.31	11.864%	$78.6516	$78.65	$78.65	$78.70
Purchase #6	$81.56	8.745%	$88.6924	$88.69	$88.70	$88.70
Purchase #7	$150.52	6.769%	$160.7087	$160.71	$160.70	$160.70
7 purchase totals =	$777.34		$852.2605	$852.26	$852.30	$852.30