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	$166.48	3.608%	$172.4866	$172.49	$172.50	$172.50
Purchase #2	$106.89	3.510%	$110.6418	$110.64	$110.65	$110.60
Purchase #3	$178.54	5.757%	$188.8185	$188.82	$188.80	$188.80
Purchase #4	$110.46	4.852%	$115.8195	$115.82	$115.80	$115.80
Purchase #5	$78.45	11.710%	$87.6365	$87.64	$87.65	$87.60
Purchase #6	$130.39	9.210%	$142.3989	$142.40	$142.40	$142.40
Purchase #7	$57.39	4.254%	$59.8314	$59.83	$59.85	$59.80
7 purchase totals =	$828.60		$877.6332	$877.64	$877.65	$877.50