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	$99.43	13.374%	$112.7278	$112.73	$112.75	$112.70
Purchase #2	$58.52	11.407%	$65.1954	$65.20	$65.20	$65.20
Purchase #3	$71.93	9.624%	$78.8525	$78.85	$78.85	$78.90
Purchase #4	$112.36	5.408%	$118.4364	$118.44	$118.45	$118.40
Purchase #5	$176.46	10.312%	$194.6566	$194.66	$194.65	$194.70
Purchase #6	$91.51	9.555%	$100.2538	$100.25	$100.25	$100.30
Purchase #7	$25.53	8.131%	$27.6058	$27.61	$27.60	$27.60
7 purchase totals =	$635.74		$697.7283	$697.74	$697.75	$697.80