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	$74.45	5.773%	$78.748	$78.75	$78.75	$78.70
Purchase #2	$176.45	11.549%	$196.8282	$196.83	$196.85	$196.80
Purchase #3	$191.97	7.351%	$206.0817	$206.08	$206.10	$206.10
Purchase #4	$78.58	8.845%	$85.5304	$85.53	$85.55	$85.50
Purchase #5	$105.65	12.640%	$119.0042	$119.00	$119.00	$119.00
Purchase #6	$189.98	10.794%	$210.4864	$210.49	$210.50	$210.50
Purchase #7	$129.76	11.213%	$144.31	$144.31	$144.30	$144.30
7 purchase totals =	$946.84		$1,040.9889	$1,040.99	$1,041.05	$1,040.90