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	$92.69	8.681%	$100.7364	$100.74	$100.75	$100.70
Purchase #2	$140.27	11.476%	$156.3674	$156.37	$156.35	$156.40
Purchase #3	$6.94	7.228%	$7.4416	$7.44	$7.45	$7.40
Purchase #4	$85.42	3.114%	$88.08	$88.08	$88.10	$88.10
Purchase #5	$146.28	11.248%	$162.7336	$162.73	$162.75	$162.70
Purchase #6	$139.77	9.795%	$153.4605	$153.46	$153.45	$153.50
Purchase #7	$31.95	13.857%	$36.3773	$36.38	$36.40	$36.40
7 purchase totals =	$643.32		$705.1968	$705.20	$705.25	$705.20