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	$73.47	4.188%	$76.5469	$76.55	$76.55	$76.50
Purchase #2	$102.90	6.218%	$109.2983	$109.30	$109.30	$109.30
Purchase #3	$134.76	7.699%	$145.1352	$145.14	$145.15	$145.10
Purchase #4	$229.41	12.324%	$257.6825	$257.68	$257.70	$257.70
Purchase #5	$223.42	4.431%	$233.3197	$233.32	$233.30	$233.30
Purchase #6	$95.33	9.491%	$104.3778	$104.38	$104.40	$104.40
Purchase #7	$82.63	11.354%	$92.0118	$92.01	$92.00	$92.00
7 purchase totals =	$941.92		$1,018.3722	$1,018.38	$1,018.40	$1,018.30