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	$93.54	7.476%	$100.5331	$100.53	$100.55	$100.50
Purchase #2	$19.76	3.840%	$20.5188	$20.52	$20.50	$20.50
Purchase #3	$192.56	3.264%	$198.8452	$198.85	$198.85	$198.80
Purchase #4	$137.57	7.491%	$147.8754	$147.88	$147.90	$147.90
Purchase #5	$114.49	11.293%	$127.4194	$127.42	$127.40	$127.40
Purchase #6	$87.86	7.279%	$94.2553	$94.26	$94.25	$94.30
Purchase #7	$39.39	12.442%	$44.2909	$44.29	$44.30	$44.30
7 purchase totals =	$685.17		$733.7381	$733.75	$733.75	$733.70