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	$33.58	11.482%	$37.4357	$37.44	$37.45	$37.40
Purchase #2	$168.27	10.333%	$185.6573	$185.66	$185.65	$185.70
Purchase #3	$179.38	4.356%	$187.1938	$187.19	$187.20	$187.20
Purchase #4	$186.53	12.196%	$209.2792	$209.28	$209.30	$209.30
Purchase #5	$40.32	4.755%	$42.2372	$42.24	$42.25	$42.20
Purchase #6	$6.71	5.577%	$7.0842	$7.08	$7.10	$7.10
Purchase #7	$224.59	7.590%	$241.6364	$241.64	$241.65	$241.60
7 purchase totals =	$839.38		$910.5238	$910.53	$910.60	$910.50