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	$230.50	13.738%	$262.1661	$262.17	$262.15	$262.20
Purchase #2	$77.83	11.282%	$86.6108	$86.61	$86.60	$86.60
Purchase #3	$38.91	9.266%	$42.5154	$42.52	$42.50	$42.50
Purchase #4	$19.40	7.572%	$20.869	$20.87	$20.85	$20.90
Purchase #5	$240.71	13.628%	$273.514	$273.51	$273.50	$273.50
Purchase #6	$207.25	6.793%	$221.3285	$221.33	$221.35	$221.30
Purchase #7	$82.99	6.462%	$88.3528	$88.35	$88.35	$88.40
7 purchase totals =	$897.59		$995.3566	$995.36	$995.30	$995.40