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	$106.96	4.179%	$111.4299	$111.43	$111.45	$111.40
Purchase #2	$199.57	9.816%	$219.1598	$219.16	$219.15	$219.20
Purchase #3	$98.89	9.107%	$107.8959	$107.90	$107.90	$107.90
Purchase #4	$172.44	9.757%	$189.265	$189.27	$189.25	$189.30
Purchase #5	$148.67	5.316%	$156.5733	$156.57	$156.55	$156.60
Purchase #6	$143.81	10.249%	$158.5491	$158.55	$158.55	$158.50
Purchase #7	$51.77	3.200%	$53.4266	$53.43	$53.45	$53.40
7 purchase totals =	$922.11		$996.2996	$996.31	$996.30	$996.30