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	$79.57	3.635%	$82.4624	$82.46	$82.45	$82.50
Purchase #2	$159.33	5.115%	$167.4797	$167.48	$167.50	$167.50
Purchase #3	$222.77	4.676%	$233.1867	$233.19	$233.20	$233.20
Purchase #4	$53.75	5.178%	$56.5332	$56.53	$56.55	$56.50
Purchase #5	$34.55	8.545%	$37.5023	$37.50	$37.50	$37.50
Purchase #6	$152.38	6.745%	$162.658	$162.66	$162.65	$162.70
Purchase #7	$165.72	6.425%	$176.3675	$176.37	$176.35	$176.40
7 purchase totals =	$868.07		$916.1898	$916.19	$916.20	$916.30