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	$69.79	4.214%	$72.731	$72.73	$72.75	$72.70
Purchase #2	$90.73	9.122%	$99.0064	$99.01	$99.00	$99.00
Purchase #3	$234.66	5.221%	$246.9116	$246.91	$246.90	$246.90
Purchase #4	$141.55	12.781%	$159.6415	$159.64	$159.65	$159.60
Purchase #5	$118.92	4.656%	$124.4569	$124.46	$124.45	$124.50
Purchase #6	$197.25	10.836%	$218.624	$218.62	$218.60	$218.60
Purchase #7	$151.80	7.149%	$162.6522	$162.65	$162.65	$162.70
7 purchase totals =	$1,004.70		$1,084.0236	$1,084.02	$1,084.00	$1,084.00