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	$196.50	10.650%	$217.4273	$217.43	$217.45	$217.40
Purchase #2	$32.40	3.304%	$33.4705	$33.47	$33.45	$33.50
Purchase #3	$248.29	12.818%	$280.1158	$280.12	$280.10	$280.10
Purchase #4	$177.62	10.844%	$196.8811	$196.88	$196.90	$196.90
Purchase #5	$91.66	7.138%	$98.2027	$98.20	$98.20	$98.20
Purchase #6	$23.43	13.861%	$26.6776	$26.68	$26.70	$26.70
Purchase #7	$166.74	11.304%	$185.5883	$185.59	$185.60	$185.60
7 purchase totals =	$936.64		$1,038.3633	$1,038.37	$1,038.40	$1,038.40