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	$44.44	9.391%	$48.6134	$48.61	$48.60	$48.60
Purchase #2	$122.94	6.634%	$131.0958	$131.10	$131.10	$131.10
Purchase #3	$113.58	10.315%	$125.2958	$125.30	$125.30	$125.30
Purchase #4	$6.94	3.663%	$7.1942	$7.19	$7.20	$7.20
Purchase #5	$92.82	6.307%	$98.6742	$98.67	$98.65	$98.70
Purchase #6	$85.82	5.350%	$90.4114	$90.41	$90.40	$90.40
Purchase #7	$94.33	5.294%	$99.3238	$99.32	$99.30	$99.30
7 purchase totals =	$560.87		$600.6086	$600.60	$600.55	$600.60