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	$72.93	4.580%	$76.2702	$76.27	$76.25	$76.30
Purchase #2	$149.33	7.216%	$160.1057	$160.11	$160.10	$160.10
Purchase #3	$116.89	4.870%	$122.5825	$122.58	$122.60	$122.60
Purchase #4	$135.90	5.826%	$143.8175	$143.82	$143.80	$143.80
Purchase #5	$68.60	5.614%	$72.4512	$72.45	$72.45	$72.50
Purchase #6	$250.26	5.334%	$263.6089	$263.61	$263.60	$263.60
Purchase #7	$120.80	6.408%	$128.5409	$128.54	$128.55	$128.50
7 purchase totals =	$914.71		$967.3769	$967.38	$967.35	$967.40