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	$132.98	5.492%	$140.2833	$140.28	$140.30	$140.30
Purchase #2	$48.46	9.596%	$53.1102	$53.11	$53.10	$53.10
Purchase #3	$109.85	13.688%	$124.8863	$124.89	$124.90	$124.90
Purchase #4	$29.96	7.441%	$32.1893	$32.19	$32.20	$32.20
Purchase #5	$75.81	12.501%	$85.287	$85.29	$85.30	$85.30
Purchase #6	$223.88	7.871%	$241.5016	$241.50	$241.50	$241.50
Purchase #7	$56.84	4.496%	$59.3955	$59.40	$59.40	$59.40
7 purchase totals =	$677.78		$736.6532	$736.66	$736.70	$736.70