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	$140.35	9.295%	$153.3955	$153.40	$153.40	$153.40
Purchase #2	$210.87	5.354%	$222.16	$222.16	$222.15	$222.20
Purchase #3	$148.79	9.368%	$162.7286	$162.73	$162.75	$162.70
Purchase #4	$129.35	12.819%	$145.9314	$145.93	$145.95	$145.90
Purchase #5	$105.44	6.727%	$112.5329	$112.53	$112.55	$112.50
Purchase #6	$106.55	12.686%	$120.0669	$120.07	$120.05	$120.10
Purchase #7	$112.29	10.333%	$123.8929	$123.89	$123.90	$123.90
7 purchase totals =	$953.64		$1,040.7082	$1,040.71	$1,040.75	$1,040.70