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	$171.97	11.528%	$191.7947	$191.79	$191.80	$191.80
Purchase #2	$5.81	9.206%	$6.3449	$6.34	$6.35	$6.30
Purchase #3	$36.31	4.387%	$37.9029	$37.90	$37.90	$37.90
Purchase #4	$181.80	5.198%	$191.25	$191.25	$191.25	$191.30
Purchase #5	$77.74	6.706%	$82.9532	$82.95	$82.95	$83.00
Purchase #6	$50.88	11.502%	$56.7322	$56.73	$56.75	$56.70
Purchase #7	$142.92	10.598%	$158.0667	$158.07	$158.05	$158.10
7 purchase totals =	$667.43		$725.0446	$725.03	$725.05	$725.10