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	$185.77	3.511%	$192.2924	$192.29	$192.30	$192.30
Purchase #2	$88.73	7.236%	$95.1505	$95.15	$95.15	$95.20
Purchase #3	$230.97	4.269%	$240.8301	$240.83	$240.85	$240.80
Purchase #4	$230.46	7.139%	$246.9125	$246.91	$246.90	$246.90
Purchase #5	$99.58	4.296%	$103.858	$103.86	$103.85	$103.90
Purchase #6	$72.56	7.202%	$77.7858	$77.79	$77.80	$77.80
Purchase #7	$214.85	13.354%	$243.5411	$243.54	$243.55	$243.50
7 purchase totals =	$1,122.92		$1,200.3704	$1,200.37	$1,200.40	$1,200.40