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	$170.51	5.695%	$180.2205	$180.22	$180.20	$180.20
Purchase #2	$250.91	4.653%	$262.5848	$262.58	$262.60	$262.60
Purchase #3	$177.91	5.467%	$187.6363	$187.64	$187.65	$187.60
Purchase #4	$80.61	3.571%	$83.4886	$83.49	$83.50	$83.50
Purchase #5	$152.76	12.684%	$172.1361	$172.14	$172.15	$172.10
Purchase #6	$30.67	7.629%	$33.0098	$33.01	$33.00	$33.00
Purchase #7	$217.52	7.145%	$233.0618	$233.06	$233.05	$233.10
7 purchase totals =	$1,080.89		$1,152.1379	$1,152.14	$1,152.15	$1,152.10