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	$166.47	6.429%	$177.1724	$177.17	$177.15	$177.20
Purchase #2	$110.34	11.851%	$123.4164	$123.42	$123.40	$123.40
Purchase #3	$101.61	13.777%	$115.6088	$115.61	$115.60	$115.60
Purchase #4	$122.97	13.532%	$139.6103	$139.61	$139.60	$139.60
Purchase #5	$85.30	7.715%	$91.8809	$91.88	$91.90	$91.90
Purchase #6	$192.50	4.236%	$200.6543	$200.65	$200.65	$200.70
Purchase #7	$223.32	10.436%	$246.6257	$246.63	$246.65	$246.60
7 purchase totals =	$1,002.51		$1,094.9688	$1,094.97	$1,094.95	$1,095.00