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	$111.40	9.844%	$122.3662	$122.37	$122.35	$122.40
Purchase #2	$74.81	4.793%	$78.3956	$78.40	$78.40	$78.40
Purchase #3	$180.90	11.695%	$202.0563	$202.06	$202.05	$202.10
Purchase #4	$59.67	5.271%	$62.8152	$62.82	$62.80	$62.80
Purchase #5	$136.89	3.639%	$141.8714	$141.87	$141.85	$141.90
Purchase #6	$190.49	10.718%	$210.9067	$210.91	$210.90	$210.90
Purchase #7	$224.68	11.671%	$250.9024	$250.90	$250.90	$250.90
7 purchase totals =	$978.84		$1,069.3138	$1,069.33	$1,069.25	$1,069.40