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	$193.41	13.821%	$220.1412	$220.14	$220.15	$220.10
Purchase #2	$151.30	11.686%	$168.9809	$168.98	$169.00	$169.00
Purchase #3	$138.50	4.173%	$144.2796	$144.28	$144.30	$144.30
Purchase #4	$56.61	4.749%	$59.2984	$59.30	$59.30	$59.30
Purchase #5	$198.26	10.229%	$218.54	$218.54	$218.55	$218.50
Purchase #6	$24.78	12.686%	$27.9236	$27.92	$27.90	$27.90
Purchase #7	$144.69	11.724%	$161.6535	$161.65	$161.65	$161.70
7 purchase totals =	$907.55		$1,000.8172	$1,000.81	$1,000.85	$1,000.80