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	$114.86	4.405%	$119.9196	$119.92	$119.90	$119.90
Purchase #2	$226.84	8.150%	$245.3275	$245.33	$245.35	$245.30
Purchase #3	$30.35	8.520%	$32.9358	$32.94	$32.95	$32.90
Purchase #4	$209.98	10.449%	$231.9208	$231.92	$231.90	$231.90
Purchase #5	$180.39	5.861%	$190.9627	$190.96	$190.95	$191.00
Purchase #6	$121.47	5.182%	$127.7646	$127.76	$127.75	$127.80
Purchase #7	$138.81	3.726%	$143.9821	$143.98	$144.00	$144.00
7 purchase totals =	$1,022.70		$1,092.8131	$1,092.81	$1,092.80	$1,092.80