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	$73.25	8.326%	$79.3488	$79.35	$79.35	$79.30
Purchase #2	$153.90	6.722%	$164.2452	$164.25	$164.25	$164.20
Purchase #3	$35.75	4.342%	$37.3023	$37.30	$37.30	$37.30
Purchase #4	$87.56	10.264%	$96.5472	$96.55	$96.55	$96.50
Purchase #5	$30.69	10.134%	$33.8001	$33.80	$33.80	$33.80
Purchase #6	$208.59	11.858%	$233.3246	$233.32	$233.30	$233.30
Purchase #7	$84.42	9.586%	$92.5125	$92.51	$92.50	$92.50
7 purchase totals =	$674.16		$737.0807	$737.08	$737.05	$736.90