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	$169.48	4.289%	$176.749	$176.75	$176.75	$176.70
Purchase #2	$105.67	3.832%	$109.7193	$109.72	$109.70	$109.70
Purchase #3	$234.73	8.770%	$255.3158	$255.32	$255.30	$255.30
Purchase #4	$192.61	10.837%	$213.4831	$213.48	$213.50	$213.50
Purchase #5	$57.38	6.245%	$60.9634	$60.96	$60.95	$61.00
Purchase #6	$63.73	12.818%	$71.8989	$71.90	$71.90	$71.90
Purchase #7	$96.31	3.431%	$99.6144	$99.61	$99.60	$99.60
7 purchase totals =	$919.91		$987.7439	$987.74	$987.70	$987.70