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	$119.59	3.501%	$123.7768	$123.78	$123.80	$123.80
Purchase #2	$75.38	6.182%	$80.04	$80.04	$80.05	$80.00
Purchase #3	$173.96	12.864%	$196.3382	$196.34	$196.35	$196.30
Purchase #4	$111.61	13.343%	$126.5021	$126.50	$126.50	$126.50
Purchase #5	$111.88	6.348%	$118.9821	$118.98	$119.00	$119.00
Purchase #6	$234.50	10.454%	$259.0146	$259.01	$259.00	$259.00
Purchase #7	$124.35	7.200%	$133.3032	$133.30	$133.30	$133.30
7 purchase totals =	$951.27		$1,037.9570	$1,037.95	$1,038.00	$1,037.90