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	$152.53	13.258%	$172.7524	$172.75	$172.75	$172.80
Purchase #2	$77.91	7.284%	$83.585	$83.59	$83.60	$83.60
Purchase #3	$162.41	5.451%	$171.263	$171.26	$171.25	$171.30
Purchase #4	$196.52	6.206%	$208.716	$208.72	$208.70	$208.70
Purchase #5	$146.87	12.193%	$164.7779	$164.78	$164.80	$164.80
Purchase #6	$238.66	12.841%	$269.3063	$269.31	$269.30	$269.30
Purchase #7	$114.63	3.805%	$118.9917	$118.99	$119.00	$119.00
7 purchase totals =	$1,089.53		$1,189.3923	$1,189.40	$1,189.40	$1,189.50