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	$82.29	7.752%	$88.6691	$88.67	$88.65	$88.70
Purchase #2	$178.48	12.318%	$200.4652	$200.47	$200.45	$200.50
Purchase #3	$230.31	3.696%	$238.8223	$238.82	$238.80	$238.80
Purchase #4	$151.97	3.764%	$157.6902	$157.69	$157.70	$157.70
Purchase #5	$48.71	8.764%	$52.9789	$52.98	$53.00	$53.00
Purchase #6	$190.26	13.700%	$216.3256	$216.33	$216.35	$216.30
Purchase #7	$232.25	5.565%	$245.1747	$245.17	$245.15	$245.20
7 purchase totals =	$1,114.27		$1,200.1260	$1,200.13	$1,200.10	$1,200.20