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	$248.76	6.568%	$265.0986	$265.10	$265.10	$265.10
Purchase #2	$248.98	9.871%	$273.5568	$273.56	$273.55	$273.60
Purchase #3	$167.88	13.384%	$190.3491	$190.35	$190.35	$190.30
Purchase #4	$83.50	6.188%	$88.667	$88.67	$88.65	$88.70
Purchase #5	$106.42	9.515%	$116.5459	$116.55	$116.55	$116.50
Purchase #6	$7.66	12.526%	$8.6195	$8.62	$8.60	$8.60
Purchase #7	$130.47	9.361%	$142.6833	$142.68	$142.70	$142.70
7 purchase totals =	$993.67		$1,085.5202	$1,085.53	$1,085.50	$1,085.50