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	$243.54	4.868%	$255.3955	$255.40	$255.40	$255.40
Purchase #2	$128.85	10.631%	$142.548	$142.55	$142.55	$142.50
Purchase #3	$208.61	6.782%	$222.7579	$222.76	$222.75	$222.80
Purchase #4	$35.79	3.702%	$37.1149	$37.11	$37.10	$37.10
Purchase #5	$41.77	11.110%	$46.4106	$46.41	$46.40	$46.40
Purchase #6	$110.45	12.856%	$124.6495	$124.65	$124.65	$124.60
Purchase #7	$109.98	7.327%	$118.0382	$118.04	$118.05	$118.00
7 purchase totals =	$878.99		$946.9146	$946.92	$946.90	$946.80