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	$68.52	5.743%	$72.4551	$72.46	$72.45	$72.50
Purchase #2	$237.72	11.431%	$264.8938	$264.89	$264.90	$264.90
Purchase #3	$118.60	12.459%	$133.3764	$133.38	$133.40	$133.40
Purchase #4	$65.66	8.759%	$71.4112	$71.41	$71.40	$71.40
Purchase #5	$120.98	4.874%	$126.8766	$126.88	$126.90	$126.90
Purchase #6	$53.76	9.839%	$59.0494	$59.05	$59.05	$59.00
Purchase #7	$97.41	7.409%	$104.6271	$104.63	$104.65	$104.60
7 purchase totals =	$762.65		$832.6896	$832.70	$832.75	$832.70