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	$153.44	7.441%	$164.8575	$164.86	$164.85	$164.90
Purchase #2	$101.65	4.239%	$105.9589	$105.96	$105.95	$106.00
Purchase #3	$28.41	11.105%	$31.5649	$31.56	$31.55	$31.60
Purchase #4	$126.79	13.150%	$143.4629	$143.46	$143.45	$143.50
Purchase #5	$41.68	8.860%	$45.3728	$45.37	$45.35	$45.40
Purchase #6	$247.57	7.567%	$266.3036	$266.30	$266.30	$266.30
Purchase #7	$30.72	10.416%	$33.9198	$33.92	$33.90	$33.90
7 purchase totals =	$730.26		$791.4404	$791.43	$791.35	$791.60