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	$201.79	13.788%	$229.6128	$229.61	$229.60	$229.60
Purchase #2	$130.47	5.273%	$137.3497	$137.35	$137.35	$137.30
Purchase #3	$172.62	13.779%	$196.4053	$196.41	$196.40	$196.40
Purchase #4	$42.39	9.762%	$46.5281	$46.53	$46.55	$46.50
Purchase #5	$178.58	10.827%	$197.9149	$197.91	$197.90	$197.90
Purchase #6	$142.45	3.801%	$147.8645	$147.86	$147.85	$147.90
Purchase #7	$99.88	13.306%	$113.17	$113.17	$113.15	$113.20
7 purchase totals =	$968.18		$1,068.8453	$1,068.84	$1,068.80	$1,068.80