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	$69.27	13.693%	$78.7551	$78.76	$78.75	$78.80
Purchase #2	$162.77	3.638%	$168.6916	$168.69	$168.70	$168.70
Purchase #3	$144.70	3.700%	$150.0539	$150.05	$150.05	$150.10
Purchase #4	$43.27	11.287%	$48.1539	$48.15	$48.15	$48.20
Purchase #5	$66.68	10.208%	$73.4867	$73.49	$73.50	$73.50
Purchase #6	$222.50	12.418%	$250.1301	$250.13	$250.15	$250.10
Purchase #7	$240.89	5.486%	$254.1052	$254.11	$254.10	$254.10
7 purchase totals =	$950.08		$1,023.3765	$1,023.38	$1,023.40	$1,023.50