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	$64.41	8.578%	$69.9351	$69.94	$69.95	$69.90
Purchase #2	$40.25	7.737%	$43.3641	$43.36	$43.35	$43.40
Purchase #3	$34.73	13.308%	$39.3519	$39.35	$39.35	$39.40
Purchase #4	$41.82	9.850%	$45.9393	$45.94	$45.95	$45.90
Purchase #5	$41.52	9.714%	$45.5533	$45.55	$45.55	$45.60
Purchase #6	$186.53	4.193%	$194.3512	$194.35	$194.35	$194.40
Purchase #7	$238.36	7.108%	$255.3026	$255.30	$255.30	$255.30
7 purchase totals =	$647.62		$693.7975	$693.79	$693.80	$693.90