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	$31.85	10.755%	$35.2755	$35.28	$35.30	$35.30
Purchase #2	$190.29	12.354%	$213.7984	$213.80	$213.80	$213.80
Purchase #3	$121.91	3.725%	$126.4511	$126.45	$126.45	$126.50
Purchase #4	$9.89	4.751%	$10.3599	$10.36	$10.35	$10.40
Purchase #5	$130.59	4.407%	$136.3451	$136.35	$136.35	$136.30
Purchase #6	$99.28	12.170%	$111.3624	$111.36	$111.35	$111.40
Purchase #7	$179.84	5.809%	$190.2869	$190.29	$190.30	$190.30
7 purchase totals =	$763.65		$823.8793	$823.89	$823.90	$824.00