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	$173.37	3.138%	$178.8104	$178.81	$178.80	$178.80
Purchase #2	$156.75	11.331%	$174.5113	$174.51	$174.50	$174.50
Purchase #3	$157.51	6.134%	$167.1717	$167.17	$167.15	$167.20
Purchase #4	$85.39	5.175%	$89.8089	$89.81	$89.80	$89.80
Purchase #5	$242.29	9.185%	$264.5443	$264.54	$264.55	$264.50
Purchase #6	$58.85	9.252%	$64.2948	$64.29	$64.30	$64.30
Purchase #7	$95.86	13.306%	$108.6151	$108.62	$108.60	$108.60
7 purchase totals =	$970.02		$1,047.7565	$1,047.75	$1,047.70	$1,047.70