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	$47.58	13.778%	$54.1356	$54.14	$54.15	$54.10
Purchase #2	$143.28	12.280%	$160.8748	$160.87	$160.85	$160.90
Purchase #3	$81.99	4.624%	$85.7812	$85.78	$85.80	$85.80
Purchase #4	$160.50	4.711%	$168.0612	$168.06	$168.05	$168.10
Purchase #5	$163.52	5.482%	$172.4842	$172.48	$172.50	$172.50
Purchase #6	$82.48	11.273%	$91.778	$91.78	$91.80	$91.80
Purchase #7	$246.59	11.743%	$275.5471	$275.55	$275.55	$275.50
7 purchase totals =	$925.94		$1,008.6621	$1,008.66	$1,008.70	$1,008.70