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	$92.71	4.527%	$96.907	$96.91	$96.90	$96.90
Purchase #2	$134.92	10.781%	$149.4657	$149.47	$149.45	$149.50
Purchase #3	$48.54	12.317%	$54.5187	$54.52	$54.50	$54.50
Purchase #4	$45.51	3.232%	$46.9809	$46.98	$47.00	$47.00
Purchase #5	$30.54	3.225%	$31.5249	$31.52	$31.50	$31.50
Purchase #6	$88.32	11.248%	$98.2542	$98.25	$98.25	$98.30
Purchase #7	$140.60	6.449%	$149.6673	$149.67	$149.65	$149.70
7 purchase totals =	$581.14		$627.3187	$627.32	$627.25	$627.40