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	$62.27	11.584%	$69.4834	$69.48	$69.50	$69.50
Purchase #2	$146.85	6.404%	$156.2543	$156.25	$156.25	$156.30
Purchase #3	$147.86	11.568%	$164.9644	$164.96	$164.95	$165.00
Purchase #4	$223.81	7.264%	$240.0676	$240.07	$240.05	$240.10
Purchase #5	$146.33	13.135%	$165.5504	$165.55	$165.55	$165.60
Purchase #6	$8.50	4.270%	$8.863	$8.86	$8.85	$8.90
Purchase #7	$98.59	12.781%	$111.1908	$111.19	$111.20	$111.20
7 purchase totals =	$834.21		$916.3739	$916.36	$916.35	$916.60