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	$206.55	10.345%	$227.9176	$227.92	$227.90	$227.90
Purchase #2	$100.43	5.440%	$105.8934	$105.89	$105.90	$105.90
Purchase #3	$42.96	5.105%	$45.1531	$45.15	$45.15	$45.20
Purchase #4	$49.93	13.829%	$56.8348	$56.83	$56.85	$56.80
Purchase #5	$152.63	8.426%	$165.4906	$165.49	$165.50	$165.50
Purchase #6	$200.47	10.511%	$221.5414	$221.54	$221.55	$221.50
Purchase #7	$219.41	6.694%	$234.0973	$234.10	$234.10	$234.10
7 purchase totals =	$972.38		$1,056.9282	$1,056.92	$1,056.95	$1,056.90