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	$112.54	3.618%	$116.6117	$116.61	$116.60	$116.60
Purchase #2	$90.87	11.715%	$101.5154	$101.52	$101.50	$101.50
Purchase #3	$202.63	9.731%	$222.3479	$222.35	$222.35	$222.30
Purchase #4	$150.38	3.580%	$155.7636	$155.76	$155.75	$155.80
Purchase #5	$132.68	7.725%	$142.9295	$142.93	$142.95	$142.90
Purchase #6	$10.30	9.233%	$11.251	$11.25	$11.25	$11.30
Purchase #7	$92.82	11.295%	$103.304	$103.30	$103.30	$103.30
7 purchase totals =	$792.22		$853.7231	$853.72	$853.70	$853.70