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	$245.71	11.781%	$274.6571	$274.66	$274.65	$274.70
Purchase #2	$109.49	7.722%	$117.9448	$117.94	$117.95	$117.90
Purchase #3	$59.83	6.480%	$63.707	$63.71	$63.70	$63.70
Purchase #4	$86.44	3.550%	$89.5086	$89.51	$89.50	$89.50
Purchase #5	$217.59	13.270%	$246.4642	$246.46	$246.45	$246.50
Purchase #6	$89.45	10.708%	$99.0283	$99.03	$99.05	$99.00
Purchase #7	$165.82	3.823%	$172.1593	$172.16	$172.15	$172.20
7 purchase totals =	$974.33		$1,063.4693	$1,063.47	$1,063.45	$1,063.50