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	$148.33	13.446%	$168.2745	$168.27	$168.25	$168.30
Purchase #2	$64.38	4.722%	$67.42	$67.42	$67.40	$67.40
Purchase #3	$149.72	6.738%	$159.8081	$159.81	$159.80	$159.80
Purchase #4	$183.83	10.642%	$203.3932	$203.39	$203.40	$203.40
Purchase #5	$219.72	7.620%	$236.4627	$236.46	$236.45	$236.50
Purchase #6	$181.54	10.287%	$200.215	$200.22	$200.20	$200.20
Purchase #7	$163.71	9.507%	$179.2739	$179.27	$179.25	$179.30
7 purchase totals =	$1,111.23		$1,214.8474	$1,214.84	$1,214.75	$1,214.90