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	$101.38	9.495%	$111.006	$111.01	$111.00	$111.00
Purchase #2	$193.32	13.400%	$219.2249	$219.22	$219.20	$219.20
Purchase #3	$246.51	11.218%	$274.1635	$274.16	$274.15	$274.20
Purchase #4	$98.68	11.180%	$109.7124	$109.71	$109.70	$109.70
Purchase #5	$134.51	6.174%	$142.8146	$142.81	$142.80	$142.80
Purchase #6	$165.34	10.841%	$183.2645	$183.26	$183.25	$183.30
Purchase #7	$48.81	5.530%	$51.5092	$51.51	$51.50	$51.50
7 purchase totals =	$988.55		$1,091.6951	$1,091.68	$1,091.60	$1,091.70