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	$220.43	4.478%	$230.3009	$230.30	$230.30	$230.30
Purchase #2	$38.55	4.452%	$40.2662	$40.27	$40.25	$40.30
Purchase #3	$42.47	6.704%	$45.3172	$45.32	$45.30	$45.30
Purchase #4	$94.91	8.429%	$102.91	$102.91	$102.90	$102.90
Purchase #5	$64.49	10.557%	$71.2982	$71.30	$71.30	$71.30
Purchase #6	$157.98	6.379%	$168.0575	$168.06	$168.05	$168.10
Purchase #7	$216.84	5.383%	$228.5125	$228.51	$228.50	$228.50
7 purchase totals =	$835.67		$886.6625	$886.67	$886.60	$886.70