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	$215.71	8.252%	$233.5104	$233.51	$233.50	$233.50
Purchase #2	$46.55	10.503%	$51.4391	$51.44	$51.45	$51.40
Purchase #3	$184.53	3.280%	$190.5826	$190.58	$190.60	$190.60
Purchase #4	$100.53	11.692%	$112.284	$112.28	$112.30	$112.30
Purchase #5	$174.54	8.500%	$189.3759	$189.38	$189.40	$189.40
Purchase #6	$84.67	11.135%	$94.098	$94.10	$94.10	$94.10
Purchase #7	$223.34	6.767%	$238.4534	$238.45	$238.45	$238.50
7 purchase totals =	$1,029.87		$1,109.7434	$1,109.74	$1,109.80	$1,109.80