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	$64.33	5.310%	$67.7459	$67.75	$67.75	$67.70
Purchase #2	$155.98	3.156%	$160.9027	$160.90	$160.90	$160.90
Purchase #3	$167.52	10.167%	$184.5518	$184.55	$184.55	$184.60
Purchase #4	$86.46	3.262%	$89.2803	$89.28	$89.30	$89.30
Purchase #5	$43.53	7.692%	$46.8783	$46.88	$46.90	$46.90
Purchase #6	$200.32	7.696%	$215.7366	$215.74	$215.75	$215.70
Purchase #7	$19.52	11.735%	$21.8107	$21.81	$21.80	$21.80
7 purchase totals =	$737.66		$786.9063	$786.91	$786.95	$786.90