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	$32.61	4.626%	$34.1185	$34.12	$34.10	$34.10
Purchase #2	$35.90	5.384%	$37.8329	$37.83	$37.85	$37.80
Purchase #3	$209.61	11.416%	$233.5391	$233.54	$233.55	$233.50
Purchase #4	$219.60	11.131%	$244.0437	$244.04	$244.05	$244.00
Purchase #5	$201.69	4.175%	$210.1106	$210.11	$210.10	$210.10
Purchase #6	$90.90	5.425%	$95.8313	$95.83	$95.85	$95.80
Purchase #7	$222.47	7.796%	$239.8138	$239.81	$239.80	$239.80
7 purchase totals =	$1,012.78		$1,095.2899	$1,095.28	$1,095.30	$1,095.10