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	$206.95	9.352%	$226.304	$226.30	$226.30	$226.30
Purchase #2	$81.72	6.165%	$86.758	$86.76	$86.75	$86.80
Purchase #3	$140.71	3.629%	$145.8164	$145.82	$145.80	$145.80
Purchase #4	$59.46	11.621%	$66.3698	$66.37	$66.35	$66.40
Purchase #5	$120.57	9.438%	$131.9494	$131.95	$131.95	$131.90
Purchase #6	$82.59	9.614%	$90.5302	$90.53	$90.55	$90.50
Purchase #7	$138.86	12.535%	$156.2661	$156.27	$156.25	$156.30
7 purchase totals =	$830.86		$903.9939	$904.00	$903.95	$904.00