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	$101.86	6.830%	$108.817	$108.82	$108.80	$108.80
Purchase #2	$89.26	8.314%	$96.6811	$96.68	$96.70	$96.70
Purchase #3	$208.92	6.703%	$222.9239	$222.92	$222.90	$222.90
Purchase #4	$32.93	8.179%	$35.6233	$35.62	$35.60	$35.60
Purchase #5	$247.79	13.368%	$280.9146	$280.91	$280.90	$280.90
Purchase #6	$116.43	3.600%	$120.6215	$120.62	$120.60	$120.60
Purchase #7	$179.53	6.210%	$190.6788	$190.68	$190.70	$190.70
7 purchase totals =	$976.72		$1,056.2602	$1,056.25	$1,056.20	$1,056.20