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	$56.28	11.690%	$62.8591	$62.86	$62.85	$62.90
Purchase #2	$229.84	8.867%	$250.2199	$250.22	$250.20	$250.20
Purchase #3	$219.82	10.682%	$243.3012	$243.30	$243.30	$243.30
Purchase #4	$32.45	8.244%	$35.1252	$35.13	$35.15	$35.10
Purchase #5	$131.42	3.584%	$136.1301	$136.13	$136.15	$136.10
Purchase #6	$67.52	5.627%	$71.3194	$71.32	$71.30	$71.30
Purchase #7	$200.77	6.112%	$213.0411	$213.04	$213.05	$213.00
7 purchase totals =	$938.10		$1,011.9960	$1,012.00	$1,012.00	$1,011.90