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	$180.85	8.723%	$196.6255	$196.63	$196.65	$196.60
Purchase #2	$94.52	6.831%	$100.9767	$100.98	$101.00	$101.00
Purchase #3	$82.81	9.789%	$90.9163	$90.92	$90.90	$90.90
Purchase #4	$116.36	10.303%	$128.3486	$128.35	$128.35	$128.30
Purchase #5	$22.44	7.435%	$24.1084	$24.11	$24.10	$24.10
Purchase #6	$5.92	13.401%	$6.7133	$6.71	$6.70	$6.70
Purchase #7	$103.76	3.441%	$107.3304	$107.33	$107.35	$107.30
7 purchase totals =	$606.66		$655.0192	$655.03	$655.05	$654.90