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	$176.41	11.451%	$196.6107	$196.61	$196.60	$196.60
Purchase #2	$245.97	9.314%	$268.8796	$268.88	$268.90	$268.90
Purchase #3	$154.44	8.872%	$168.1419	$168.14	$168.15	$168.10
Purchase #4	$35.66	7.271%	$38.2528	$38.25	$38.25	$38.30
Purchase #5	$228.74	10.826%	$253.5034	$253.50	$253.50	$253.50
Purchase #6	$247.32	11.349%	$275.3883	$275.39	$275.40	$275.40
Purchase #7	$5.42	12.381%	$6.0911	$6.09	$6.10	$6.10
7 purchase totals =	$1,093.96		$1,206.8678	$1,206.86	$1,206.90	$1,206.90