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	$209.38	12.685%	$235.9399	$235.94	$235.95	$235.90
Purchase #2	$115.80	6.585%	$123.4254	$123.43	$123.45	$123.40
Purchase #3	$78.83	4.855%	$82.6572	$82.66	$82.65	$82.70
Purchase #4	$172.35	11.365%	$191.9376	$191.94	$191.95	$191.90
Purchase #5	$31.46	10.671%	$34.8171	$34.82	$34.80	$34.80
Purchase #6	$141.60	3.221%	$146.1609	$146.16	$146.15	$146.20
Purchase #7	$100.47	9.528%	$110.0428	$110.04	$110.05	$110.00
7 purchase totals =	$849.89		$924.9809	$924.99	$925.00	$924.90