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	$35.62	5.666%	$37.6382	$37.64	$37.65	$37.60
Purchase #2	$60.51	6.764%	$64.6029	$64.60	$64.60	$64.60
Purchase #3	$74.41	10.344%	$82.107	$82.11	$82.10	$82.10
Purchase #4	$19.42	12.280%	$21.8048	$21.80	$21.80	$21.80
Purchase #5	$153.40	9.417%	$167.8457	$167.85	$167.85	$167.80
Purchase #6	$84.75	10.791%	$93.8954	$93.90	$93.90	$93.90
Purchase #7	$178.46	3.783%	$185.2111	$185.21	$185.20	$185.20
7 purchase totals =	$606.57		$653.1051	$653.11	$653.10	$653.00