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	$77.60	10.543%	$85.7814	$85.78	$85.80	$85.80
Purchase #2	$155.76	7.549%	$167.5183	$167.52	$167.50	$167.50
Purchase #3	$201.71	13.651%	$229.2454	$229.25	$229.25	$229.20
Purchase #4	$92.86	9.634%	$101.8061	$101.81	$101.80	$101.80
Purchase #5	$152.48	12.545%	$171.6086	$171.61	$171.60	$171.60
Purchase #6	$159.36	8.104%	$172.2745	$172.27	$172.25	$172.30
Purchase #7	$106.71	12.204%	$119.7329	$119.73	$119.75	$119.70
7 purchase totals =	$946.48		$1,047.9672	$1,047.97	$1,047.95	$1,047.90