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	$76.40	5.506%	$80.6066	$80.61	$80.60	$80.60
Purchase #2	$61.77	6.653%	$65.8796	$65.88	$65.90	$65.90
Purchase #3	$247.88	6.614%	$264.2748	$264.27	$264.25	$264.30
Purchase #4	$138.50	13.314%	$156.9399	$156.94	$156.95	$156.90
Purchase #5	$143.37	10.275%	$158.1013	$158.10	$158.10	$158.10
Purchase #6	$219.45	8.563%	$238.2415	$238.24	$238.25	$238.20
Purchase #7	$125.87	5.774%	$133.1377	$133.14	$133.15	$133.10
7 purchase totals =	$1,013.24		$1,097.1814	$1,097.18	$1,097.20	$1,097.10