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	$160.62	5.718%	$169.8043	$169.80	$169.80	$169.80
Purchase #2	$205.72	4.315%	$214.5968	$214.60	$214.60	$214.60
Purchase #3	$82.72	12.313%	$92.9053	$92.91	$92.90	$92.90
Purchase #4	$31.57	6.133%	$33.5062	$33.51	$33.50	$33.50
Purchase #5	$202.36	7.195%	$216.9198	$216.92	$216.90	$216.90
Purchase #6	$37.43	7.596%	$40.2732	$40.27	$40.25	$40.30
Purchase #7	$70.28	10.302%	$77.5202	$77.52	$77.50	$77.50
7 purchase totals =	$790.70		$845.5258	$845.53	$845.45	$845.50