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	$64.94	11.393%	$72.3386	$72.34	$72.35	$72.30
Purchase #2	$89.58	13.144%	$101.3544	$101.35	$101.35	$101.40
Purchase #3	$193.55	11.815%	$216.4179	$216.42	$216.40	$216.40
Purchase #4	$213.96	3.263%	$220.9415	$220.94	$220.95	$220.90
Purchase #5	$181.29	10.699%	$200.6862	$200.69	$200.70	$200.70
Purchase #6	$147.63	3.549%	$152.8694	$152.87	$152.85	$152.90
Purchase #7	$78.93	9.568%	$86.482	$86.48	$86.50	$86.50
7 purchase totals =	$969.88		$1,051.0900	$1,051.09	$1,051.10	$1,051.10