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	$249.41	13.409%	$282.8534	$282.85	$282.85	$282.90
Purchase #2	$206.92	7.655%	$222.7597	$222.76	$222.75	$222.80
Purchase #3	$202.90	5.113%	$213.2743	$213.27	$213.25	$213.30
Purchase #4	$64.38	11.571%	$71.8294	$71.83	$71.85	$71.80
Purchase #5	$134.57	8.323%	$145.7703	$145.77	$145.75	$145.80
Purchase #6	$29.97	4.380%	$31.2827	$31.28	$31.30	$31.30
Purchase #7	$166.41	5.205%	$175.0716	$175.07	$175.05	$175.10
7 purchase totals =	$1,054.56		$1,142.8414	$1,142.83	$1,142.80	$1,143.00