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	$236.44	3.390%	$244.4553	$244.46	$244.45	$244.50
Purchase #2	$46.73	8.124%	$50.5263	$50.53	$50.55	$50.50
Purchase #3	$106.80	11.517%	$119.1002	$119.10	$119.10	$119.10
Purchase #4	$91.99	8.653%	$99.9499	$99.95	$99.95	$99.90
Purchase #5	$29.83	5.615%	$31.505	$31.51	$31.50	$31.50
Purchase #6	$50.91	4.855%	$53.3817	$53.38	$53.40	$53.40
Purchase #7	$214.62	6.493%	$228.5553	$228.56	$228.55	$228.60
7 purchase totals =	$777.32		$827.4737	$827.49	$827.50	$827.50