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	$47.61	12.679%	$53.6465	$53.65	$53.65	$53.60
Purchase #2	$181.49	8.294%	$196.5428	$196.54	$196.55	$196.50
Purchase #3	$62.74	8.324%	$67.9625	$67.96	$67.95	$68.00
Purchase #4	$147.55	4.269%	$153.8489	$153.85	$153.85	$153.80
Purchase #5	$105.71	5.138%	$111.1414	$111.14	$111.15	$111.10
Purchase #6	$20.54	4.517%	$21.4678	$21.47	$21.45	$21.50
Purchase #7	$14.67	9.402%	$16.0493	$16.05	$16.05	$16.00
7 purchase totals =	$580.31		$620.6592	$620.66	$620.65	$620.50