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	$213.73	8.435%	$231.7581	$231.76	$231.75	$231.80
Purchase #2	$6.79	7.599%	$7.306	$7.31	$7.30	$7.30
Purchase #3	$190.61	7.812%	$205.5005	$205.50	$205.50	$205.50
Purchase #4	$242.82	11.603%	$270.9944	$270.99	$271.00	$271.00
Purchase #5	$89.72	11.269%	$99.8305	$99.83	$99.85	$99.80
Purchase #6	$118.87	7.341%	$127.5962	$127.60	$127.60	$127.60
Purchase #7	$189.77	12.687%	$213.8461	$213.85	$213.85	$213.80
7 purchase totals =	$1,052.31		$1,156.8318	$1,156.84	$1,156.85	$1,156.80