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	$170.88	5.681%	$180.5877	$180.59	$180.60	$180.60
Purchase #2	$83.88	7.704%	$90.3421	$90.34	$90.35	$90.30
Purchase #3	$34.41	7.113%	$36.8576	$36.86	$36.85	$36.90
Purchase #4	$230.44	5.693%	$243.5589	$243.56	$243.55	$243.60
Purchase #5	$201.88	12.672%	$227.4622	$227.46	$227.45	$227.50
Purchase #6	$152.54	4.759%	$159.7994	$159.80	$159.80	$159.80
Purchase #7	$219.89	3.423%	$227.4168	$227.42	$227.40	$227.40
7 purchase totals =	$1,093.92		$1,166.0247	$1,166.03	$1,166.00	$1,166.10