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	$225.29	10.801%	$249.6236	$249.62	$249.60	$249.60
Purchase #2	$146.32	12.710%	$164.9173	$164.92	$164.90	$164.90
Purchase #3	$195.61	11.708%	$218.512	$218.51	$218.50	$218.50
Purchase #4	$139.45	4.636%	$145.9149	$145.91	$145.90	$145.90
Purchase #5	$86.64	12.745%	$97.6823	$97.68	$97.70	$97.70
Purchase #6	$165.39	8.571%	$179.5656	$179.57	$179.55	$179.60
Purchase #7	$107.46	4.340%	$112.1238	$112.12	$112.10	$112.10
7 purchase totals =	$1,066.16		$1,168.3395	$1,168.33	$1,168.25	$1,168.30