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	$199.51	12.437%	$224.3231	$224.32	$224.30	$224.30
Purchase #2	$221.26	3.493%	$228.9886	$228.99	$229.00	$229.00
Purchase #3	$110.38	12.761%	$124.4656	$124.47	$124.45	$124.50
Purchase #4	$55.77	11.710%	$62.3007	$62.30	$62.30	$62.30
Purchase #5	$104.90	4.435%	$109.5523	$109.55	$109.55	$109.60
Purchase #6	$144.38	12.827%	$162.8996	$162.90	$162.90	$162.90
Purchase #7	$107.25	4.337%	$111.9014	$111.90	$111.90	$111.90
7 purchase totals =	$943.45		$1,024.4313	$1,024.43	$1,024.40	$1,024.50