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	$71.48	8.597%	$77.6251	$77.63	$77.65	$77.60
Purchase #2	$237.73	9.123%	$259.4181	$259.42	$259.40	$259.40
Purchase #3	$86.76	10.195%	$95.6052	$95.61	$95.60	$95.60
Purchase #4	$84.30	9.455%	$92.2706	$92.27	$92.25	$92.30
Purchase #5	$184.49	6.467%	$196.421	$196.42	$196.40	$196.40
Purchase #6	$149.78	3.381%	$154.8441	$154.84	$154.85	$154.80
Purchase #7	$59.97	12.326%	$67.3619	$67.36	$67.35	$67.40
7 purchase totals =	$874.51		$943.5460	$943.55	$943.50	$943.50