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	$161.62	6.767%	$172.5568	$172.56	$172.55	$172.60
Purchase #2	$243.48	8.430%	$264.0054	$264.01	$264.00	$264.00
Purchase #3	$78.63	6.236%	$83.5334	$83.53	$83.55	$83.50
Purchase #4	$250.89	9.343%	$274.3307	$274.33	$274.35	$274.30
Purchase #5	$159.72	6.697%	$170.4164	$170.42	$170.40	$170.40
Purchase #6	$109.81	3.499%	$113.6523	$113.65	$113.65	$113.70
Purchase #7	$19.77	5.356%	$20.8289	$20.83	$20.85	$20.80
7 purchase totals =	$1,023.92		$1,099.3239	$1,099.33	$1,099.35	$1,099.30