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	$201.80	13.178%	$228.3932	$228.39	$228.40	$228.40
Purchase #2	$240.56	13.473%	$272.9706	$272.97	$272.95	$273.00
Purchase #3	$65.63	8.798%	$71.4041	$71.40	$71.40	$71.40
Purchase #4	$75.86	3.580%	$78.5758	$78.58	$78.60	$78.60
Purchase #5	$246.89	5.519%	$260.5159	$260.52	$260.50	$260.50
Purchase #6	$57.64	13.305%	$65.309	$65.31	$65.30	$65.30
Purchase #7	$61.76	7.842%	$66.6032	$66.60	$66.60	$66.60
7 purchase totals =	$950.14		$1,043.7718	$1,043.77	$1,043.75	$1,043.80