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	$95.66	10.682%	$105.8784	$105.88	$105.90	$105.90
Purchase #2	$161.69	5.688%	$170.8869	$170.89	$170.90	$170.90
Purchase #3	$131.63	12.444%	$148.01	$148.01	$148.00	$148.00
Purchase #4	$219.33	6.366%	$233.2925	$233.29	$233.30	$233.30
Purchase #5	$142.67	4.752%	$149.4497	$149.45	$149.45	$149.40
Purchase #6	$80.59	9.314%	$88.0962	$88.10	$88.10	$88.10
Purchase #7	$204.55	4.363%	$213.4745	$213.47	$213.45	$213.50
7 purchase totals =	$1,036.12		$1,109.0882	$1,109.09	$1,109.10	$1,109.10