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	$158.89	13.275%	$179.9826	$179.98	$180.00	$180.00
Purchase #2	$82.80	3.123%	$85.3858	$85.39	$85.40	$85.40
Purchase #3	$174.54	4.248%	$181.9545	$181.95	$181.95	$182.00
Purchase #4	$46.87	5.603%	$49.4961	$49.50	$49.50	$49.50
Purchase #5	$212.89	4.287%	$222.0166	$222.02	$222.00	$222.00
Purchase #6	$68.47	6.766%	$73.1027	$73.10	$73.10	$73.10
Purchase #7	$245.70	3.103%	$253.3241	$253.32	$253.30	$253.30
7 purchase totals =	$990.16		$1,045.2624	$1,045.26	$1,045.25	$1,045.30