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	$222.96	3.190%	$230.0724	$230.07	$230.05	$230.10
Purchase #2	$112.94	13.484%	$128.1688	$128.17	$128.15	$128.20
Purchase #3	$147.64	11.599%	$164.7648	$164.76	$164.75	$164.80
Purchase #4	$146.94	13.757%	$167.1545	$167.15	$167.15	$167.20
Purchase #5	$7.29	4.723%	$7.6343	$7.63	$7.65	$7.60
Purchase #6	$32.88	13.579%	$37.3448	$37.34	$37.35	$37.30
Purchase #7	$115.80	4.252%	$120.7238	$120.72	$120.70	$120.70
7 purchase totals =	$786.45		$855.8634	$855.84	$855.80	$855.90