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	$175.97	6.572%	$187.5347	$187.53	$187.55	$187.50
Purchase #2	$50.94	5.370%	$53.6755	$53.68	$53.70	$53.70
Purchase #3	$78.55	11.651%	$87.7019	$87.70	$87.70	$87.70
Purchase #4	$161.88	4.152%	$168.6013	$168.60	$168.60	$168.60
Purchase #5	$85.99	4.488%	$89.8492	$89.85	$89.85	$89.80
Purchase #6	$146.71	12.130%	$164.5059	$164.51	$164.50	$164.50
Purchase #7	$23.30	8.376%	$25.2516	$25.25	$25.25	$25.30
7 purchase totals =	$723.34		$777.1201	$777.12	$777.15	$777.10