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	$179.29	7.160%	$192.1272	$192.13	$192.15	$192.10
Purchase #2	$73.79	6.378%	$78.4963	$78.50	$78.50	$78.50
Purchase #3	$187.66	10.465%	$207.2986	$207.30	$207.30	$207.30
Purchase #4	$79.77	3.218%	$82.337	$82.34	$82.35	$82.30
Purchase #5	$21.83	7.797%	$23.5321	$23.53	$23.55	$23.50
Purchase #6	$185.51	4.792%	$194.3996	$194.40	$194.40	$194.40
Purchase #7	$173.67	13.123%	$196.4607	$196.46	$196.45	$196.50
7 purchase totals =	$901.52		$974.6515	$974.66	$974.70	$974.60