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	$197.63	6.538%	$210.551	$210.55	$210.55	$210.60
Purchase #2	$216.45	12.324%	$243.1253	$243.13	$243.15	$243.10
Purchase #3	$183.67	6.866%	$196.2808	$196.28	$196.30	$196.30
Purchase #4	$96.71	3.741%	$100.3279	$100.33	$100.35	$100.30
Purchase #5	$186.42	4.313%	$194.4603	$194.46	$194.45	$194.50
Purchase #6	$116.96	9.769%	$128.3858	$128.39	$128.40	$128.40
Purchase #7	$175.94	10.552%	$194.5052	$194.51	$194.50	$194.50
7 purchase totals =	$1,173.78		$1,267.6363	$1,267.65	$1,267.70	$1,267.70