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	$192.35	6.374%	$204.6104	$204.61	$204.60	$204.60
Purchase #2	$130.86	9.704%	$143.5587	$143.56	$143.55	$143.60
Purchase #3	$37.67	7.335%	$40.4331	$40.43	$40.45	$40.40
Purchase #4	$75.76	6.765%	$80.8852	$80.89	$80.90	$80.90
Purchase #5	$248.72	3.226%	$256.7437	$256.74	$256.75	$256.70
Purchase #6	$224.36	3.546%	$232.3158	$232.32	$232.30	$232.30
Purchase #7	$199.52	5.409%	$210.312	$210.31	$210.30	$210.30
7 purchase totals =	$1,109.24		$1,168.8589	$1,168.86	$1,168.85	$1,168.80