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	$91.53	10.747%	$101.3667	$101.37	$101.35	$101.40
Purchase #2	$232.25	13.141%	$262.77	$262.77	$262.75	$262.80
Purchase #3	$196.58	12.233%	$220.6276	$220.63	$220.65	$220.60
Purchase #4	$17.96	3.160%	$18.5275	$18.53	$18.55	$18.50
Purchase #5	$182.28	4.526%	$190.53	$190.53	$190.55	$190.50
Purchase #6	$61.54	4.400%	$64.2478	$64.25	$64.25	$64.20
Purchase #7	$113.33	6.658%	$120.8755	$120.88	$120.90	$120.90
7 purchase totals =	$895.47		$978.9451	$978.96	$979.00	$978.90