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	$133.72	5.455%	$141.0144	$141.01	$141.00	$141.00
Purchase #2	$129.91	5.706%	$137.3227	$137.32	$137.30	$137.30
Purchase #3	$148.74	13.857%	$169.3509	$169.35	$169.35	$169.40
Purchase #4	$95.41	5.462%	$100.6213	$100.62	$100.60	$100.60
Purchase #5	$131.93	8.495%	$143.1375	$143.14	$143.15	$143.10
Purchase #6	$17.58	5.798%	$18.5993	$18.60	$18.60	$18.60
Purchase #7	$165.76	10.608%	$183.3438	$183.34	$183.35	$183.30
7 purchase totals =	$823.05		$893.3899	$893.38	$893.35	$893.30