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	$243.92	12.629%	$274.7247	$274.72	$274.70	$274.70
Purchase #2	$95.34	5.365%	$100.455	$100.46	$100.45	$100.50
Purchase #3	$8.88	6.682%	$9.4734	$9.47	$9.45	$9.50
Purchase #4	$180.80	4.705%	$189.3066	$189.31	$189.30	$189.30
Purchase #5	$105.45	13.566%	$119.7553	$119.76	$119.75	$119.80
Purchase #6	$250.95	3.471%	$259.6605	$259.66	$259.65	$259.70
Purchase #7	$102.73	5.642%	$108.526	$108.53	$108.55	$108.50
7 purchase totals =	$988.07		$1,061.9015	$1,061.91	$1,061.85	$1,062.00