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	$226.94	12.246%	$254.7311	$254.73	$254.75	$254.70
Purchase #2	$38.28	8.811%	$41.6529	$41.65	$41.65	$41.70
Purchase #3	$87.70	3.148%	$90.4608	$90.46	$90.45	$90.50
Purchase #4	$129.52	3.508%	$134.0636	$134.06	$134.05	$134.10
Purchase #5	$187.38	4.759%	$196.2974	$196.30	$196.30	$196.30
Purchase #6	$142.70	11.222%	$158.7138	$158.71	$158.70	$158.70
Purchase #7	$153.46	10.336%	$169.3216	$169.32	$169.30	$169.30
7 purchase totals =	$965.98		$1,045.2412	$1,045.23	$1,045.20	$1,045.30