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	$157.76	9.165%	$172.2187	$172.22	$172.20	$172.20
Purchase #2	$166.95	12.165%	$187.2595	$187.26	$187.25	$187.30
Purchase #3	$250.93	7.134%	$268.8313	$268.83	$268.85	$268.80
Purchase #4	$52.42	4.550%	$54.8051	$54.81	$54.80	$54.80
Purchase #5	$32.74	13.105%	$37.0306	$37.03	$37.05	$37.00
Purchase #6	$75.87	9.327%	$82.9464	$82.95	$82.95	$82.90
Purchase #7	$193.62	8.737%	$210.5366	$210.54	$210.55	$210.50
7 purchase totals =	$930.29		$1,013.6282	$1,013.64	$1,013.65	$1,013.50