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	$105.90	3.552%	$109.6616	$109.66	$109.65	$109.70
Purchase #2	$83.66	10.568%	$92.5012	$92.50	$92.50	$92.50
Purchase #3	$203.31	9.807%	$223.2486	$223.25	$223.25	$223.20
Purchase #4	$128.38	7.173%	$137.5887	$137.59	$137.60	$137.60
Purchase #5	$30.33	9.515%	$33.2159	$33.22	$33.20	$33.20
Purchase #6	$152.34	4.354%	$158.9729	$158.97	$158.95	$159.00
Purchase #7	$19.96	4.442%	$20.8466	$20.85	$20.85	$20.80
7 purchase totals =	$723.88		$776.0355	$776.04	$776.00	$776.00