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	$177.95	10.232%	$196.1578	$196.16	$196.15	$196.20
Purchase #2	$120.36	3.802%	$124.9361	$124.94	$124.95	$124.90
Purchase #3	$133.36	4.164%	$138.9131	$138.91	$138.90	$138.90
Purchase #4	$101.52	12.520%	$114.2303	$114.23	$114.25	$114.20
Purchase #5	$10.69	10.704%	$11.8343	$11.83	$11.85	$11.80
Purchase #6	$124.28	13.262%	$140.762	$140.76	$140.75	$140.80
Purchase #7	$103.44	5.865%	$109.5068	$109.51	$109.50	$109.50
7 purchase totals =	$771.60		$836.3404	$836.34	$836.35	$836.30