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	$89.41	13.541%	$101.517	$101.52	$101.50	$101.50
Purchase #2	$165.57	5.614%	$174.8651	$174.87	$174.85	$174.90
Purchase #3	$87.53	7.856%	$94.4064	$94.41	$94.40	$94.40
Purchase #4	$118.42	7.582%	$127.3986	$127.40	$127.40	$127.40
Purchase #5	$171.41	9.690%	$188.0196	$188.02	$188.00	$188.00
Purchase #6	$210.85	13.305%	$238.9036	$238.90	$238.90	$238.90
Purchase #7	$124.70	10.794%	$138.1601	$138.16	$138.15	$138.20
7 purchase totals =	$967.89		$1,063.2704	$1,063.28	$1,063.20	$1,063.30