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	$141.78	7.713%	$152.7155	$152.72	$152.70	$152.70
Purchase #2	$74.31	5.456%	$78.3644	$78.36	$78.35	$78.40
Purchase #3	$39.25	13.119%	$44.3992	$44.40	$44.40	$44.40
Purchase #4	$206.98	7.805%	$223.1348	$223.13	$223.15	$223.10
Purchase #5	$69.34	4.160%	$72.2245	$72.22	$72.20	$72.20
Purchase #6	$234.50	11.586%	$261.6692	$261.67	$261.65	$261.70
Purchase #7	$231.33	12.169%	$259.4805	$259.48	$259.50	$259.50
7 purchase totals =	$997.49		$1,091.9881	$1,091.98	$1,091.95	$1,092.00