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	$89.88	12.737%	$101.328	$101.33	$101.35	$101.30
Purchase #2	$109.61	5.805%	$115.9729	$115.97	$115.95	$116.00
Purchase #3	$17.62	13.163%	$19.9393	$19.94	$19.95	$19.90
Purchase #4	$41.86	4.334%	$43.6742	$43.67	$43.65	$43.70
Purchase #5	$92.64	3.700%	$96.0677	$96.07	$96.05	$96.10
Purchase #6	$188.30	10.805%	$208.6458	$208.65	$208.65	$208.60
Purchase #7	$74.79	9.487%	$81.8853	$81.89	$81.90	$81.90
7 purchase totals =	$614.70		$667.5132	$667.52	$667.50	$667.50